
Book bl_l^_ 



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CfiEffilGHT DEPOSm 



THE LOCATION, 

GRADING AND DRAINAGE 

OF HIGHWAYS 



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PU5LISHER.S OF 



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THE LOCATION, 
GRADING AND DRAINAGE 

OF HIGHWAYS 

A Concise Discussion of General Principles Illustrated 
by Current and Recommended Practice 



BY 

WILSON G. HARGER, C.E. 

ENGINEER NEW YOEK STATE DEPARTMENT OF HIGHWAYS; FORMER 

SENIOR HIGHWAY ENGINEER, UNITED STATES OFFICE OF ROADS. 

AUTHOR OF "highway ENGINEERS* HANDBOOK," ETC. 



First Edition 



McGRAW-HILL BOOK COMPANY, Inc. 

NEW YORK: 370 SEVENTH AVENUE 

LONDON: 6 & 8 BOUVERIE ST., E. C. 4 

1921 






\^Z^ ' 



copyeight, 1921, bt the 
McGraw-Hill Book Compaxy, Inc. 



THE MAPLE PRESS YOHK PA 



APR -4 1321 
g)C!,A611467 



PREFACE 

This book is the first of a series of four volumes presenting the 
road problem from the standpoint of the constructing engineer. 
It is intended for the use of students and practicing engineers. 
Each book will be complete in itself and will deal with a well 
defined portion of the general problem. 

The first book covers a discussion of general principles govern- 
ing the policy of highway programs such as: the scope of the 
program, general character of the system, classification, layout, 
appropriation estimates, fundamental principles of design and 
reasonable economy in design. It develops the detail theory of 
economic location and grade line design from the standpoints of 
both horse and motor traffic. It discusses Cross Sections, 
Roadway Widths, Right of Way and Drainage. The intention 
is for this volume to cover concisely but fully the principles of 
design of the relatively permanent features of highway construc- 
tion. Theory is developed but used largely as a basis for judge- 
ment. The data and discussions of theory are made as definite 
as possible and are illustrated by current and recommended 
practice. Emphasis is laid on the desirability of making appro- 
priations accomplish as much as possible and the engineering 
means to this end are indicated. An effort has been made to 
show the value and limitations of scientific engineering in relation 
to the road problem. 

The other volumes of the series are in preparation. They will 
cover the selection of pavement type, methods of construction. 
Maintenance and Reconstruction; also the detail methods of 
field and office work and Construction Engineering and 
Inspection. 

The co-operation of Highway Engineers and State Departments 
is acknowledged throughout the text. Special acknowledge- 
ment is made of the constructive criticism of this manuscript by 
Mr. Percy Waller, Mr. Thomas Mahaney, Mr. J. Y. McChntock 
and Mr. H. G. Hotchkiss. 

A number of tables and some of the text have been adapted 
from the Harger and Bonney Highway Engineers' Handbook. 

W. G. Harger. 
Rochester, N. Y., 1920. 

vii 



CONTENTS 

Page 

Preface vii 

Chapter 1. General Principles of Economic Highway Design . . 1-27 

The relation of highway engineering to the road problem ... 1 

The value of reasonably complete mileage (Road Service) . . 4 

The necessity of traffic regulation 9 

Relative importance of local and long distance traffic 10 

General character of traffic 10 

General basis for pavement foundation and bridge design ... 12 

General basis for selection of pavement type 14 

General basis for pavement width . 15 

General basis for safety provisions 17 

Economic use of road materials 17 

General methods of financing (Effect on Design) 20 

Contract relations 23 

General maintenance problem 24 

Summary of general principles 26 

Conclusion 27 

Chapter 2. Proportion and Economy in Design 28-35 

Relative importance of the detail elements of design 28 

General solutions (highway design) 30-31 

Pioneer districts 30 

Well settled districts 31 

Reasonable economy in design 31-35 

Review of current design 31 

Systematic economies 33 

Tests of designs. . . ■ 33 

Order of work 35 

Preliminary investigations .35 

Surveys 35 

Office design 35 

Conclusion 35 

Chapter 3. Classification, Route and General Engineering Location 38-66 

The layout of road systems _ 38 

Classification of roads 40-52 

For financing 41 

National roads 41 

State roads 42 

County roads 42 

Town roads 42 

ix 



X TABLE OF CONTENTS 

. Page 
Classification of roads (Cont.) 

For design , 42 

By location 43 

By traffic census 43 

Example of Classification 

For design (Pavement Type) 46 

For appropriation estimates 49 

For maintenance and renewal financing 51 

General Distribution of tax burden 52 

Tables of serial bond costs 50 

Prevailing general tax rates 51 

Order of construction of projects 55 

Selection of route 55-58 

General principles 55 

Examples 56-58 

Well settled district 56 

Pioneer district . 58 

Engineering location 59-67 

Desirable features 59 

Extreme refinements impracticable 60 

Value of saving distance and rise 63 

Relocations of existing highways 64 

Conclusion 66 

Chapter 4. Grades and Alignment 68-150 

Effect of grades 68 

Maximum Grades 69-125 

Relative importance of horse and motor traffic in the selection 

of grades 69 

The effect of horse traffic on maximum grade 71-80 

Safety of descent . 71 

Ascent 

Hauling power 72 

Grade resistance 73 

Rolling resistance 73 

Comparison of loads on grades 75 

Effect of length of grade on maximum load 77 

Records of maximum team loads 78 

Theoretical advantages of certain grades 79 

The effect of motor operation costs on grade line design . 80-114 

Ascent & descent 80 

Chart of climbing power 82 

Convenience of operation 81 

Mechanical energy climbing 83 

Value of distance saved 86 

Value of rise saved 86 

Distance balanced against rise 92 

Approx. cost motor operation on different grades ... 96 

Comparison of alternate locations . . . • 96-107 

Comparison of cut and fill profiles 107-114 



TABLE OF CONTENTS xi 

Page 

Summary of motor traffic considerations 113 

Effect of maintenance cost on maximum grade 114 

Effect of safe footing on maximum grade 114 

Effect of farm team hauling on maximum grade 114 

Effect of construction cost on maximum grade 115 

Maximum grades in present use 115 

Recommended practice (maximum grades) 116 

Unusually high rates of grade 117 

Consistent maximum rates 117 

Effect of maximum grade on cost ' . . 118 

Intermediate Grades 125-129 

Their value 125 

Their effect on cost 126 

The ''rolling grade" ' . . 126 

Effect of arbitrary profile limitations on cost . ...... 129 

Minimum Grades 

Hard pavements 129 

Earth roads 130 

Adverse Grades .' 130 

Vertical Curves 

Effect of sight distance 131 

Recommended practice 131 

WTien used 131 

Minimum length 132 

Summary of Grades 132 

Alignment 133-147 

General discussion 133 

Dangerous alignment 134 

Effect of "Sight Distance" 134 

Current practice minimum curvature 136 

Effect of long wheel base rigs 138 

Effect of alignment on grade 138 

Effect of alignment on motor operation costs 141 

Effect of alignment on construction cost 142 

Effect of railroad grade crossings on alignment and grade . . 144 

Recommended alignment practice 147 

Conclusion of Chapter . 148-150 

Summary of principles of location 148 

Summary of principles of cut and fill 149 

Chapter 5. Cross Sections of Rural Roads, Widths of Pavement, 

Right of Way Clearing 151-211 

General considerations 151 

Sections (High type roads) 

Premises of design 152 

Widths of traveled way 153 

Depth of ditches 157 

Effect of grading width on cost 159 

Stable cut and fill slopes 160 



xii TABLE OF CONTENTS 

Page 

Pavement widths 162-167 

Effect on cost 162 

Widths in use 163 

Effect of curves 165 

Amount of widening 165 

Amount of superelevation 167 

Examples of current practice. . . .' 168-177 

Examples of recommended practice 178-181 

Sections (Mountain Roads) 182-208 

Discussion 182 

Crown *....' 182 

Widths of section (effect on cost) 183 

Minimum width 185 

Turnouts 189 

Fill sections 191 

Through cut 191 

Selection of section 192 

Examples of typical sections 194-208 

Summary of sections 208 

Right of way and clearing widths 208 

Effect of sidewalks 209 

Effects of tree planting 209 

Effects of sight distance 210 

Effects of grading 210 

Effect of clearing 211 

Recommended practice 211 

Chapter 6. Drainage 212-270 

Classification 212 

Cross drainage 212-262 

Considerations in design ' . 213 

Location 214 

Area of waterway 218 

Grade and elevation of inverts 229 

Minimum cushion 230 

Dead and live loads 230 

Length of structure ' . . . 231 

Economical type of structure 233 

Relative cost of culverts 238 

Examples of current practice (culverts) 239-247 

Small span bridges 248-261 

Foundation soils 248 

Pile loadings 248 

Scour 262 

Examples current practice 249-261 

Longitudinal drainage 262-267 

Ditches 262 

Carrying capacity* 262 

Protection from scour 264 



TABLE OF CONTENTS xiii 

Page 
Ditches {Cont.) 

Current practice 264 

Storm sewers • 265 

Drivewa}^ culverts 266 

Under drainage 267 

Summary of chapter 269 

Conclusion of Volume I 270 

Appendix A, Highway Bonds 271-278 



THE LOCATION, 

GRADING AND DRAINAGE 

OF HIGHWAYS 

CHAPTER I 

GENERAL PRINCIPLES OF ECONOMIC HIGHWAY 

DESIGN 

The Relation of Highway Engineering to The Road Prob- 
lem. — The advantages of improved highways have been so well 
demonstrated that it is not at all difficult to inaugurate improve- 
ment programs up to the limit of the financial ability of the com- 
munities. The reasonable expenditure of appropriations for the 
actual construction of roads is the pressing problem at this time. 
From political, business and engineering standpoints it is essen- 
tial that highway programs shall not be discredited. 

Construction work should fulfil as nearly as possible the prom- 
ises made at the time the appropriation is authorized as these 
promises are in essence a contract with the community, which if 
not carried out in good faith react on the promoters and dis- 
credit the road movement. The community generally expects 
a reasonable mileage of serviceable road. If appropriation esti- 
mates are based on careful engineering layouts, classifications 
and cost estimates, the finished construction will usually approxi- 
mate the proposed program. If no such engineering advice is 
used the completed work often falls far short of what the tax- 
payers have a right to expect. 

A pohcy of uniform pavement design utilizing one type of 
pavement to the extent of excluding other standard and well- 
recognized types is to be avoided. A distribution of patronage 
among the various business interests actively engaged in road 
construction promotes healthy competition and eliminates the 
needless antagonism of those industries which might be slighted 
under a uniform policy. Such a distribution of business results 
from an engineering analysis of the selection of pavement type, 

1 



2 LOCATION, GRADIXG AXD DRAIXAGE OF HIGHWAYS 

as common sense engineering tends to discourage any policy of 
uniform pavement selection, not only on account of the danger 
of raising prices, overloading the capacity of special road material 
industries, overloading transportation facilities, and slowing down 
construction progress, but also because various Idnds of pavement 
are needed to meet different road conditions. 

Road programs are always subjected to partisan criticism. If 
they are based on sound engineering principles and the con- 
struction controlled by rigid engineering inspection, they are 
easier to defend and are changed less by successive administra- 
tions. The tendency of new administrations to needlessly change 
pohcy and methods in the midst of a construction program 
rarely works out well and while it is impossible to entirely pre- 
vent this, any method that helps to stabilize procedure is a move 
in the right direction. Even from the standpoint of ordinary 
political expediency reliable engineering is useful. 

The value of broad gauge engineering as a basis for highway 
work is so evident to anyone famiHar with the problem that it 
ought to be generally recognized. Unfortunately it is often not 
given the weight to which it is entitled. This is partly due to 
popular prejudice and is partly the fault of the engineering pro- 
fession. The average citizen and many non-technical road 
officials consider that the engineer is an unavoidable nuisance 
and that whatever is spent on engineering is a doubtful invest- 
ment. They feel that for some reason an engineer is necessary, 
but they are hazy as to why this is so. They are impressed by 
the use of a transit or level, but have no respect for broad engi- 
neering decisions. They think because roads are a common every 
day affair that the highway problem is simple and requires no 
special training. They know that local officials have built most 
of the roads of the past and see no reason for the scientific anal- 
ysis of the road problem in the future. They have the local 
view point of the old piecemeal temporary light traffic programs, 
which were fairly well handled by local men, and they have no 
real conception of a unified modern highway system with its 
range of traffic from hght duty to heavy duty. They do not 
differentiate between the value of mediocre and high-grade 
engineering; they know that almost anyone can build almost 
any kind of a road if money enough is provided, but they do not 
reaHze that the test of high grade engineering hes in the actual 
construction of a proper road for less money than would be spent 



ECONOMIC HIGHWAY DESIGN 3 

by a less expert designer. This point of view can be corrected 
by effort on the part of the engineers and while it handicaps the 
work at present it adds interest to the game which would other- 
wise be too easy. As a matter of fact the rapid adoption of 
State and Federal control of highway programs automatically 
improves the engineering and financial aspects, although the 
status of highway engineers is yet far below what it should be. 
Even the pubHc officials who realize the value of high-grade 
technical advice either have to consider the popular view or 
actually prefer mediocre talent on account of lower salaries and 
the greater freedom that they have to carry out their own pet 
schemes. 

No profession can achieve a high standing unless its members 
demonstrate a sense of responsibility to the community. In 
highway work it seems reasonable to hold the engineer responsi- 
ble for the general scheme and the detail results. If a program 
is essentially wrong no one knows it better than the engineer 
and no one can point out the constructive remedy better than 
he can. If he chooses to subordinate his knowledge and sense 
of responsibiUty to policies of political expediency affecting the 
fundamental value of the improvements the entire profession 
pays the penalty. If he is content to be a tool he will be treated 
as a tool. If he has the mental attitude of a subordinate clerk 
or office boy, he will be ranked as such. The fighting spirit in 
regard to real essentials is necessary. It is strictly up to the 
profession. They must throw their influence towards sound 
finance programs. They must insist on first class construction 
and the fair treatment of contractors. They must not advocate 
scientific fads and needlessly excessive refinements in materials 
or methods which raise the cost of roads beyond reason. They 
must be as careful not to overdesign as not to underdesign. 
They must realize their responsibility to the community at large, 
but not overemphasize the strictly technical part of a highway 
program. 

Any sound engineering pohcy is based on good common 
sense which emphasizes the fact that highway engineering and 
even the actual construction of roads are only a means to an 
end. The most important people in any road program are the 
actual road users who serve the community by the operation of 
vehicles over the completed highways. The actual traffic in- 
terests are the most important factor in any proper solution. 



4 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

It is essential that traffic requirements be carefully analyzed and 
that caution be used in excessive expenditures for the benefit, 
of a small percentage of the actual road users. That is, the re- 
quirements of the average road user should usually outweigh 
the spectacular requirements of a small number of men, unless 
these men are wilHng to pay the additional cost of construction 
made necessary by the unusual type of vehicle which they 
operate. 

The highw^ay problem is extremely complex and subject to a 
wide range of local conditions which affect the detail solutions 
but the general principles are fairly well defined. There are a 
number of satisfactory ways of solving the details of any 
problem, provided the general plan is sound and economic 
principles of design are apphed. The important thing is that a 
comprehensive analysis shall be made and some well-balanced 
plan carried to a conclusion. 

DISCUSSION OF GENERAL PRINCIPLES 

The intent of the general discussion is to emphasize the main 
features of design. For this reason, fine distinctions are not in- 
troduced in this chapter as they tend to confuse the argument. 
Before taking up the detail analysis it is just as w^ell to make a 
quick survey of the general factors governing policy and to formu- 
late a few fundamental principles on which the scheme of design 
can be developed. 

Road Service. — Service to the community and to the direct 
user is the object of all road improvements. It is not uncommon 
for Highway Engineers to forget the road user and the community 
and think only of a mass of technical detail. Service to the 
community consists in aiding the improvement of economic and 
social conditions of rural hfe and in promoting the development 
of natural resources. Service to the direct road user hes in pro- 
viding a means whereby he can get all the way to his destination in 
comparative safety and at the same time haul his load. Roads 
are intended to get somewhere and not to stop on the way. The 
fundamental requirement of all highway programs would seem 
to be the construction of the greatest possible connected mileage 
of road that will handle existing traffic without too large a main- 
tenance charge. The entire problem of economic design is 
founded on this premise. 

It is not unusual to see large appropriations absorbed by a com- 



ECONOMIC HIGHWAY DESIGN 5 

paratively small mileage of magnificent roads when the commu- 
nity apparently needs a larger mileage of good usable highways. 
It is self evident that service consists more in adequate connected 
mileage of moderate priced roads for a large percentage of the 
distance and high priced roads where actually needed than it 
does in a shorter mileage of nothing but boulevards. The first 




Fig. 2. — A wagon trail (Montana) . The first stage of pioneer road improvement. 

principle of design may therefore be stated as: the construction of 
the greatest possible mileage of connected roads of a type suitable 
to the stage of development of the community and its existing traffic. 
Mileage is the first and foremost factor of service. Needlessly 
short mileage is the most serious criticism that can be made of 
any general policy dealing with an incomplete road system. 
The practical appUcation of this principle eliminates all non- 



6 LOCATION, GRADING AND DRAINAGE OP HIGHWAYS 





YzG. 3. — ^ell built natural soil roads. The seccr_~ 

provement (Pioneer Dis^ricis 



:e Oi progressive im- 



ECONOMIC HIGHWAY DESIGN 7 

essential expenditure but encourages necessary expenditures on 
essential features. To illustrate we may say that a reasonable 
policy of service requires radically different methods of approach 
in different localities. Road design ranges from the low-type 
earth roads of sparsely settled districts to the hard-surfaced pave- 
ments of densely populated sections. For these extreme condi- 
tions the issues are clear-cut; the first requires the greatest 
possible mileage with hmited funds, and the last the most suitable 
design /or present conditions regardless of first cost. Intermediate 
cases are handled by merging the requirements of the extremes. 
A reasonable design for any case depends on the needs and re- 



FiG. 4. — Typical single track gravel road (New York state) . Very satisfactory 
for local traffic in agricultural districts. (The third stage of progressive im- 
provement.) 

sources of the local community, considered in connection with the 
importance of the improvement to the general transportation 
scheme of the country and the outside aid that will be granted 
on account of its general importance. In pioneer districts mile- 
age is the only important consideration, and a sufficiently cheap 
type of construction must be adopted to obtain a hne of communi- 
cation to the point desired; an ordinary earth road is all that can 
be reasonably expected for the greater part of these districts. 
Scattered agricultural communities require primarily roads that 
are usable the year around and that will handle ordinary farm 
traffic; gravel or similar, fairly cheap constructions are the only 
reasonable solutions for the greater part of these districts. 



8 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Densely populated districts with closely located cities require the 
highest, strongest type of rigid pavements for the main connecting 
routes and macadam and gravel constructions for the secondary 
and local roads. 

To design a needlessly expensive road even in a rich community 
is as poor pohcy as to build a road that will not handle the present 
traffic. It is not necessary to worry about future traffic. The 
future has a habit of taldng care of itself. The permanent fea- 
tures of construction such as route, ahgnment, grades, etc. 
should be designed for the future but the pavement surface is at 
its best only temporary and extremely expensive pavements are 




Fig. 5. — Typical penetration bituminous macadam (State Route No. 16 
New York). Carries approximately 1500 vehicles per day. Note the easy 
shoulder slope which adds to the safetj^ of traffic. 

not justified unless present traffic demands them. Appropria- 
tions for the original construction of improved highways over 
routes on which the existing roads are poor may well be spent on 
the principle of mileage service. After a system of reasonably 
good roads is attained a Reconstruction Program of Boulevards 
is justified if the money is available from the proper sources. 
The community at large can generally afford to shoulder the burden 
of the original construction of reasonably good roads but it can rarely 
afford to pay for boulevards. The direct road user can well afford 
to shoulder the burden of the maintenance of reasonably good roads 
and he should be given the opportunity of paying for reconstruction 
if he wants the additional comfort and ease of a boidevard system. 



ECONOMIC HIGHWAY DESIGN 



Some conclusion of this nature governs the decision as to the 
method of J&nancing various stages of improvement programs. 

Demands of Traffic and Their Effect on Design. — To fulfill 
the principle of service, roads should be located and designed to 
serve the great majority of direct users with the least inconvenience 
and the fewest restrictions that are feasible, but a few individuals 
who, for some reason, find it convenient to use extremely heavy 
unit vehicles, must be ruled off from the majority of the highways. 
It will be financially impossible for any community to construct 
and maintain all of its rural highways and bridges without regu- 
lation of heavy traffic. Roads hke any other engineering struc- 




FiG. 6. — Typical rigid pavement highway (Industrial District Ohio) . 
shallow ditch which adds to the safety of traffic. 



Note the 



ture should be built for normal and not for abnormal use. The 
highway engineer would prefer not to restrict traffic but it is a 
practical necessity. It is not feasible or desirable to restrict 
average traffic but we cannot permit a small percentage of the 
users to operate exceptionally heavy units which if considered 
in the design of local service roads would raise the total cost of 
a general road system beyond reason. 

The second principle of design appears to he: Traffic regulation 
is necessary not only to save past investment hut also to enable the 
community to finance any enduring general system of roads and to 
make economic engineering design possible. The application of this 
principle hinges on the usual range and popular methods of hauling. 



10 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Range of Traffic. — All the available data indicates that prob- 
ably 90 to 95 per cent, of road traffic can be classed as local 
service. That is, it has its origin and finish within a compara- 
tively short radius and consists of the hauling of garden truck 
to cities, produce to shipping points, social visits and short rec- 
reational trips. The other 10 per cent, may be classed as long 
distance traffic consisting of pleasure touring, light passenger cars 
of commercial travelers and long distance motor hauling of 
freight between cities. These ratios of general traffic do not, of 
course, apply to any one road and may be actually reversed on 
certain special touring routes but they probably apply to the 
road systems as a whole in most states, counties and towns and 
they indicate the basis for locating improvements and for appor- 
tioning county, state or federal aid. Any highway program to 
render the greatest service to the community may well be laid 
out on the principle of serving first the local and second the 
through traffic. 

It is certain that a county that adopts the policy of getting 
some kind of a road that is usable the year round in front of 
every farm is nearer right than if it spent the funds for a skeleton 
system of needlessly high-class roads routed primarily for through 
traffic. There is no reason why the program should not con- 
sider both factors in their proper proportion but the danger has 
of late years been more often on the side of favoring through 
traffic to the detriment of local service. The third principle of 
design may he formulated as: Local traffic is entitled to first con- 
sideration in the location of roads and their design except for a com- 
paratively small mileage of special service highways. To apply 
the second and third principles, it is necessary to arrive at a 
reasonable conclusion in regard to traffic routes and also as to 
what types of vehicle will probably best serve the great major- 
ity of direct road users. 

Weight of Traffic. — Twenty years ago road traffic was entirely 
horse drawn. Today it is largely motor, particularly where an 
improved road system has been completed. It is safe to say 
that highway transport on improved roads will be largely by 
motor vehicles although it is not hkely that horse traffic will 
entirely disappear. Motor traffic for commercial success re- 
quires a higher speed and greater unit vehicle load than horse 
traffic and consequently controls the foundation design and sur- 
facing of the roads of today although in some features of the design 



ECONOMIC HIGHWAY DESIGN 



11 



it is probably better to modify this conclusion in order to satisfy 
the requirements of horse traffic also. 

For the usual farming community where the hauls do not ex- 
ceed 10 to 20 miles to market or shipping points and where each 
farmer owns his truck all available information indicates that 
the light %- to 23-^-ton truck with pneumatic tire equipment 
will probably be the most popular type for hauling.^ The popu- 
larity of this type seems to be based on a reasonable first cost, 
moderate upkeep, high speed, comfort and general utility. This 
kind of truck does not seriously injure any of the improved roads 




Fig. 7. — Moderate size general utility truck. 

that are in general use provided they are well designed and main- 
tained. Such truck traffic and the usual pleasure car need not 
be subjected to regulation to the extent of modifying any of their 
desirable features. That is, probably 90 to 95 per cent, of road 
users can be served with moderate priced roads. 

For long distance motor freight hauling in competition with 
railroad freight the 5-ton or heavier truck appears to be the logical 
unit. At the present time, there does not seem to be a large 
proportion of road mileage that will be subjected to this class of 
traffic. It is, however, an increasingly important phase of serv- 
ice, but as the conditions which make it economical do not apply 

1 See U. S. Dept. of Agriculture Bulletin No. 919 for data on the use of 
trucks by farmers. 



12 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

to large areas a comparatively small number of special service 
roads ought to satisfy any reasonable demands of such users. 
Traffic of this kind requires a heavy rigid type of pavement, 
the shortest possible distance between terminals, the ehmi- 
nation of needless rise and fall, and easy grades. Special 
service roads should be built but it is reasonable to restrict the 
operation of heavy trucks or trailer trains to these routes and 
rule them off of the secondary and feeder roads. Special per- 
mits to 5-ton trucks could be granted for a special fee for emer- 
gency trips over local service roads during the dry season of the 
year. Regulations of this nature would not be an unreasonable 
hardship on the commercial interests manufacturing or using 
such units as the great field for their popularity is apparently 
confined largely to city territory or to well-defined hauhng routes. 

The tractor trailer sj^stem is apphcable to special conditions 
but reasonable gross weights and wheel pressures are not a hard- 
ship to the manufacturer or user and regulation of these outfits 
make them feasible for use on special service roads. They do 
not necessarily require a rigid pavement surface but generally do 
require a greater road foundation strength than most secondary 
or feeder roads and should be ruled off of such roads. 

It therefore seems feasible to regulate traffic to the point where 
the community can afford to build improved road systems, with- 
out unfairness to the manufacturers of trucks or annoying inter- 
ference with the choice of the individual in his car. Present 
sentiment favors the design of secondary and feeder roads on the 
basis of a 10-ton gross vehicle load, a 7-ton gross back axle load 
and a wheel pressure per hnear inch of tire not exceeding 600 lb. 
Special service roads may well be designated to carry a gross 
vehicle load of 15 tons, a 10-ton back axle load and a wheel pres- 
sure of 800 lb. per linear inch of width of tire. Practically aU 
authorities are agreed that heavy traffic must he regulated for 
both load and speed. The present sentiment on sohd tire truck 
speed regulation appears to he between 12 and 15 miles per hour; 
the effect of speed on impact and the amount of such impact on 
pavements is under investigation by the U. S. Bureau of Roads. 

The fourth principle of design may he assumed to he: the strength 
of pavement foundations and hridges should he designed for the 
maximum regulated load for the class of service for which the road 
is intended. No attempt should be made to reduce construction 
cost by using a weak foundation. 



ECONOMIC HIGHWAY DESIGN 13 

The practical action of this principle results as a rule in rigid 
pavement construction on special service roads and in some form 
of macadam, gravel, sand-clay, or earth roads for the secondary 
and feeder systems. Under certain conditions of material sup- 
ply a rigid pavement is desirable even on secondary roads but 
the case is the exception rather than the rule considering the 
first principle of design, Mileage Service. 



INFORMATION TO TRUCK OPERATORS 

The essential points in Section 1, par. 282-a of the Highway Law, 
as enacted by the New York State Legislature of 1920, are as 
follows : 

1. No truck, with load, shall weigh more than twenty-five 
thousand pounds. 

2. No truck body, including load, shall be more than eight 
feet wide. 

3. No truck body, including load, shall be more than twelve feet 
six inches high. 

4. No wheel shall carry more than eight hundred pounds per 
inch width of tire. 

NEW YORK STATE DEPARTMENT OF HIGHWAYS, 

. Fred'k Stuart Greene, 

Commissioner. 

Truck Dimensions and Loading 



Under the state law of Pennsylvania (1920) commercial vehicles 
are divided into seven classes. The maximum weights allowed for 
these classes, including chassis, body and load, are as follows: 

Class AA, 7,000 lb.; class A, 11,000 lb.; class B, 15,000 lb.; 
class C, 20,000 lb.; class D, 24,000 lb.; class C and F, 26,000 lb. 

No commercial vehicles may travel at a rate of speed in excess of 
that shown in the following table: 

Class AA, 20 miles per hour; class A, 20 miles; class B, 18 
miles; class C, 15 miles; class D, 15 miles; class E, 12 miles; class 
F, 10 miles. 

Truck Speeds 



14 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Pavement Type. — The use of different pavements for different 
service can be well shown by a quotation from a recent article 
on a general scheme of Highway Improvement in Monroe 
County, New York.^ Monroe County has an unusually good 
general highway system. J. Y. McCHntock, the County Super- 
intendent of Highways, is one of the most level headed highway 
engineers in the country today. The following material is 
briefed from his report (see Fig. 14, opposite page 42, for map of 
this territory) : 

Monroe County has an area of 650 squaremiles 

A total population of approximately 350,000 

A population, City of Rochester, approx 280,000 

A population outside of the city, approx 70,000 

An assessed valuation (real) of $327,000,000 

A total mileage of roads, outside of the city and villages of 1,360 approx. 

A total mileage of improved state roads of 330 approx. 

A total mileage of improved town roads of 700 approx. 

A total mileage of unimproved roads of 330 approx. 

The total number of motor licenses 22,000 approx. 

The total number of truck licenses 3,000 approx. 

(Approximately 85 per cent, of these trucks are less than 
2-ton rated capacity). 

The demands of traffic in this county are more extreme than 
for most localities except in metropolitan areas. The county has 
had all kinds of pavements in use under a great range of traffic 
for a number of years and we feel that we have sufficient data in 
regard to maintenance costs and the hfe of surfacings to come to a 
reasonable conclusion as to the future policy of completing the 
road system. The conclusions are summarized as fojlows: 

''We advocate the original construction of cross roads of thick modern 
waterbound macadam utilizing local materials as much as possible 
and maintained by surface oiling. 

"We advocate the original construction of our secondary radial 
roads, of penetration, bituminous macadam, utilizing local materials to 
their fullest reasonable extent and maintained by surface oiling. 

"We advocate the construction of our Main Trunk Line heavy hauling 
roads of rigid pavements, using the best materials that can be obtained, 
but varying the type to secure, in each case, the cheapest first cost 
pavement, always considering the possible use of local materials proper 
for the type of road in question. For these roads we have no choice 

^ This particular district is a rich highly developed country. For pioneer 
territory or scattered agricultural districts the same general principle applies 
but relatively cheaper road surfaces must be used. 



ECONOMIC HIGHWAY DESIGN 15 

between cement concrete, brick, sheet asphalt, asphalt block, or stone 
block on concrete bases. 

''We advocate the gradual resurfacing of the heavier traffic macadam 
roads with Topeka mix, small brick cubes, etc. We have successfully 
utilized this method in reducing high surface maintenance costs where 
the macadam foundation was solid enough for the traffic, and have 
adopted this method for a number of our roads. We have examples 
which have stood a 10 years' test successfully. 

"We believe that the community has been better served by construct- 
ing 10 miles of macadam in place of a possible 6 miles of rigid pavement. 

''We believe that the county has been better served in the past and 
will be best served in the future by variable road designs using for the 
majority of the mileage modern macadam for the original construction, 
later modified, if necessarj^, for a very limited mileage by recapping with 
a lower maintenance cost surface. We advocate rigid pavements 
eventually for, approximately, 10 per cent, of the total mileage of our 
roads and for approximately 35 per cent, of our State System." 

The fifth principle of design becomes: Vary the type of pavement 
to suit the demands of existing traffic. Avoid the use of rigid pave- 
ments on local service roads except for unusual conditions of ma- 
terial supply. 

Pavement Width. — The number and width of vehicles using 
the road controls the design of pavement width and in many 
cases the type of pavement surface. It is, however, well to 
bear in mind that, in order not to violate the first principle of 
design, namely. Mileage Service, the basis for the selection of 
width should be the expected volume of traffic in the immediate 
future and not the far distant future. It is always possible to 
widen or improve the pavement under a Maintenance or Re- 
construction program. The sixth rule of design may he stated as: 
the number of vehicles and the percentage of horse traffic govern the 
width of the pavement and its surfacing. The practical application 
of this rule may be indicated in a rough general way as follows : 

Single track pavements 8 to 12 ft. wide built of good natural 
soil materials, gravel or macadam serve very satisfactorily if 
properly maintained under a local service traffic up to about 
300 vehicles per day in the busy season. In well settled commu- 
nities a road of this kind is generally a cross road. 

Double track pavements 15 to 16 ft. wide built of thick 
modern waterbound or bituminous macadam with special shoul- 
ders if necessary will serve satisfactorily up to approximately 
1800 local service vehicles per ten-hour day in the busy season if 



16 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

properly maintained. In well settled communities a road of 
this class is generally a secondary radial road or it may constitute 
the least used portion of a main road connecting large cities 
located more than 100 miles apart. 

If traffic exceeds this amount macadam maintenance generally 
results in too much interference with traffic even if the vehicles 
are hght units although there have been cases of the successful 
use of penetration bituminous macadam up to 3500 vehicles per 
day, 300 of which were trucks. As a rule a volume of traffic of 
over 1800 rigs per ten-hour day in the busy season means that 




Fig. 8. — Tj-pical unprotected mountain road. Illustrates the necessity 
for careful driving. Continuous guard rail would be prohibitive in cost except 
on a few of the main transcontinental routes. 

the road should be classed as a special ser\dce road entitled to a 
high cost rigid pavement. Roads of this class are generally main 
roads between large cities located less than 100 miles apart or 
main Radial Roads for a distance of 5 to 40 miles from cities or 
special Industrial Roads. Rigid pavements less than 18 ft. ^ide 
are rarely satisfactory to traffic on account of the formation of 
ruts in the shoulders along the edge of the pavement. Present 
sentiment favors 20-ft. width of rigid pavements on main roads 
near cities. In very unusual cases a pavement width of 29 or 
38 ft. is desirable. 



ECONOMIC HIGHWAY DESIGN 



17 






mmmimuMm 



^ 



The relative mileage of single and double track pavements 
will, of course, vary for each locality but it is not hkely that even 
in the more populous states that more than 10*to 20 per cent, of 
the roads need to be designed as doable track roads and it is not 
probable that at the present time over 1 to 5 per cent, can be 
classed as special service roads. 

Safety and Convenience of Traffic. — The amount of money 
that it is desirable to spend on safeguards to traffic is largely con- 
trolled by the volume of traffic. 
Extreme danger should be 
avoided on any improved road 
but on the lighter travelled 
roads considerable must be 
left to the care of the driver. 
On such roads about all that 
is justified are danger signs 
and cheap guard rail that 
warn instead of actually pro- 
tecting and on many mountain 
roads even cheap guard rail is 
out of the question (see Fig. 
8). On heavy travel special 
service roads all possible safe- 
guards should be employed, 
such as the ehmination of rail- 
road grade crossings, sub- 
stantial strong concrete guard 
rail or retaining walls, widen- 
ing and banking the pavement 
on curves, a safe ''sight dis- 
tance" ahead at all times, 
shallow ditches, and warning and guide signs for the direction 
of travel. The seventh rule of design covers safety of traffic. On 
light traffic roads confine safety provisions to warnings. On heavy 
traffic routes spend all the money that is necessary to make the road 
as nearly fool proof as possible. 

Materials and Their Effect on the Selection of Pavement 
Type. — The proper use of available local road building material 
is a fundamental economic principle in road design and properly 
controls the selection of pavement type. This principle is 
rarely disregarded in small local programs where the funds are 

2 



^ 







Fig. 9, — An unusual and effective warn- 
ing sign on an unprotected road. 



18 LOCATIOS. GBADIXG AXD DBAIXAGE OF HIGHWAYS 

limited and the officials are in close contact with the taxpayer, 
or in State aid Work in the sparsely settled States where the 
funds are small. Unfortimately its Adolation is quite frequent in 
State Aid Work in the rich States committed to veiy high class 
pavement design and is probably due to the tendency of large 
state organizations to generahze too broadly both on the minimum 
acceptable requirements of materials and on the selection cf pave- 
ment type. That is, they often fail to analyze each job carefully, 
to make comparative estimates cf cost and to modify a general 
specification to make it adaptable to special conditions. They 
are working with large appropriations and have not much per- 
sonal incentive for clean cut efficiency. The proverbial drunken 
sailor is sometimes a piker in comparison. I do not mean by 
this that the roads are not well constructed for as a rule the con- 
struction is A number one and is in fact much better than that 
obtained under local control but the amoimt of money spent in 
the process is often needlessly high. It is well worth while to 
make a systematic effort to stop all the small leaks which amount 
to large figures in the aggregate. This does not mean that local 
control of Highway Design is better than State or National 
Control. We have had enough experience with both methods 
to demonstrate the very marked advantage of State and Federal 
Control in improving the general character of programs but this 
particular weakness can and ought to be corrected. 

The desirabihty of the proper use of local material does not 
seem open to argument and the eighth rule of design becomes: 
inferior material should never he used, but the type of pavement 
should be varied to permit the proper use of existing local materials 
or the cheapest iinported 7naterials. In practice this requires very 
thorough investigation of all local supphes. It necessitates a 
common sense attitude of the testing laboratory; it requires a 
reasonably flexible specffication but it results in saving more 
money than any other single detail of design. The requirements 
of materials are discussed in the second book of this series, but 
to illustrate the practical application of this principle in a 
general way a couple of possible^ cases will be outlined. 

Suppose a local service road carr^TLng approximately 400 vehi- 
cles per day is to be built. That a limited supply of coarse gravel 
is available fit for bottom course macadam construction but not 
fit for concrete pavement or concrete pa^nng base. That there 
is enough of this gravel to build a satisfactory bottom course for 



ECONOMIC HIGHWAY DESIGN ID 

1 mile of road with a short haul. Suppose at the other end of 
the road there is a local quarry of stone fit for bottom course but 
not hard enough for macadam top or concrete pavement. Under 
such conditions comparative estimates of original construction 
cost, maintenance and renewal for the different possible types will 
generally show a distinct saving in both first cost and ultimate 
cost for a macadam road utilizing the local gravel for 1 mile of 
bottom, the local stone for 3 miles of bottom and a hard imported 
stone top. Under these conditions the author has seen time and 
again either the entire elimination of the gravel if macadam is 
used or entire elimination of local materials by the adoption of 
concrete pavement for the full distance. It is against this ten- 
dency that we wish to throw the weight of existing evidence. 

Suppose a local service road handling approximately 1500 ve- 
hicles per day is to be built and that a first class local stone is 
available fit for any grade of macadam or concrete but that con- 
crete pavement sand has to be imported. Suppose that compara- 
tive estimates of construction cost show that an 18 ft. concrete 
pavement will cost only $8,000 per mile more than a satisfactory 
16 ft. Bituminous Macadam with special macadam shoulders, and 
that there are enough funds available to construct the entire length 
of the proposed improvement with concrete. Under these con- 
ditions considering the factors of life, maintenance and renewal it 
is probably desirable to select the concrete pavement. If the 
difference in cost had been say $9,000 per mile for price conditions 
prevaiHng in the year 1920 it is probable that the selection of 
Bituminous Macadam would be the proper solution The de- 
ciding point in comparative costs of different constructions will 
vary for different localities, different traffic and different years as 
discussed later but some such basis of selection must be borne 
continually in mind if you expect to give a rational explanation 
of the selection of type. Each road must be analyzed on this 
basis as it often happens that within a couple of miles of each 
other, two different roads will require entirely different conclu- 
sions. There is too much generalization in type selection. Time 
after time the author has been forced to build inadequate maca- 
dam roads because there happened to be a reaction against 
high grade pavements that particular year. This is as short- 
sighted as the opposite tendency noted above. The actual working 
out of highway programs is rarely logical as there are too many con- 
flicting interests to be considered but wherever it is possible to do 



20 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

SO a reasonable analysis should be given the selection of type. 
Type selection is also often befogged by various arguments con- 
nected with the method of financing the improvement. 






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Financing Improvements (Effect on Design). — Reasonable 
finance programs are based on the relative cost and length of life 
of the temporary and permanent features of road construction. 

Improvements are as a rule financed in one of three ways: 

1. 'Pay as you go" policy. 



ECONOMIC HIGHWAY DESIGN 



21 



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2. Serial bonds whose terms are based on the Hfe of the im- 
provement. 

3. Long term bonds (sinking 
fund method). 

The comparative total cost to 
the taxpayers of these methods 
is illustrated by Charts A and B. 
The ''Pay as you go" pohcy is, 
of course, the least expensive in 
total cost but has a number of 
drawbacks The serial bond 
method is in more favor at pre- 
sent than either the first or third 
method. The total cost to the 
taxpayer increases with the 
length of the bond term 

Long term bonds have been 
used in the past as they provided 
a more or less painless method of 
extracting the necessary money 
but the additional total cost of a 
fifty year term bond, which has 
often been used, and its evident 
fault of throwing too much of 
the burden on the future has re- 
sulted in practically eliminating 
such a long term method. Bond 
issues of some sort for the original 
construction of a highway system 
have the advantages of making 
it possible to carry out a co-ordi- 
nated scheme more easily than 
the "Pay as you go" pohcy. 
They make it easier to get a con- 
tinuous program of construction 
and to organize and operate a 
reasonably effective engineering 
organization for the design and 
construction. The serial bond 

method based on a twenty-five or thirty year term and financed 
by general tax levy seems reasonable for the original construction 




5ti S 



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22 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

of a general system of highways composed of all the different 
types of pavement that would ordinarily be used to serve the 
average road user. The ''Pay as you go" pohcy or serial bonds 
of about a fifteen year term financed by auto licenses or some 
other form of direct vehicle tax seem reasonable for a Reconstruc- 
tion Program of boulevards or special Commercial Roads. It 
is self evident that maintenance funds should be "Pay as you go'' 
and probably financed by direct vehicle taxes. 

The methods of raising road funds vary for the different 
States and are changed from year to year. The Highway Green 
Book issued yeaily by the American Auto Assoc, affords a con- 
venient reference for up to date data on road laws and methods of 
raising funds. Appendix A reprints their discussion of Highway 
Bonds. 

Reasonable bond terms are based on the following general data. 
On well built roads the pavement surfacing or resurfacing and 
other minor elements such as gutters, guide signs, etc. are the 
temporary features. The other items of work such as grading, 
well built culverts, and foundations are relatively permanent. 
The top course of double track macadam type roads use up as a 
rule from 40 to 50 per cent, of the total cost of original construc- 
tion and last from 8 to 12 years on local service roads before a 
new top course is necessary. That is, the deterioration of 
macadam roads can be assumed to be 40 per cent, in ten years and 
after that time there is very little further deterioration of the 
original construction. The resurfacing of rigid type of pavement 
can be assumed to cost about 60 per cent, of the total original 
cost of the road and resurfacing is generally required in from 
15 to 20 years. The deterioration for such roads can be assumed 
roughly as 60 per cent, in 15 years after which there is very little 
further depreciation on the original investment. 

Any scheme of financing which pays off 40 per cent, of the 
original loan in 10 years and 60 per cent, in 15 years appears 
reasonable for any general improvement program covering roads 
of different types. The twenty five year serial bond accom- 
plishes this making it possible to reconstruct these pavement sur- 
facings at the proper time without pyramiding loans. For 
reconstruction programs, however, the term should not exceed 
15 years as the total expenditure is on temporary features. 

Programs based on 50 year bond issues can not by any ex- 
pedient of the engineer be made reasonable from the standpoint 



ECONOMIC HIGHWAY DESIGN 23 

of the relation of the Hfe of the surfacing to the term of the bond 
but this fact should not influence the engineer in his choice cf 
pavement type if he has to work under such a bond issue. The 
following attitude has had considerable pubhcity. "If our bonds 
are 50 year bonds, build oiu* roads to last for 50 years. Build 
Permanent Pavements. Build Concrete or Brick or Sheet 
Asphalt (depending on the business connections of the speaker)." 
As a matter of fact no large mileage of concrete will last for 50 
years without resurfacing, neither will brick, neither will sheet 
asphalt, neither will macadam. As a matter of fact, the only 
road that does not need resurfacing in 50 years is a natural earth 
road. 

Why therefore cut down needed mileage and reduce mileage 
service, the first principle of design, by the use of rigid pavements 
on side roads where there is no engineering justification for 
them. A well designed macadam road under traffic for which 
it is suited will not cost any more for 50 years including mainte- 
nance, renewals, and interest on first cost than a rigid pavement 
on the same road. A long bond term never justified the use of 
rigid pavements on local service roads and the ninth rule of 
design becomes: Every effort should he made to obtain a reasonable 
term of bond but if a long term is used, do not permit the term of 
bond issue under which the improvement is made to influence the 
selection of pavement type. 

Contract -Relations. — Assuming that the road is well designed 
it is necessary to get it well built. Sound business relations be- 
tween contractors and the directing engineering organizations is 
manifestly the only possible means of getting good work at a 
reasonable cost. Any element of unnecessary risk or uncer- 
tainty which the contractor must assume raises the bid price of 
the work. Any doubt as to whether the work will be let provided 
a reasonable bid is secured tends to keep away responsible con- 
tractors. Prompt decision and uniform treatment are essential. 
Reasonable profits are necessary to insure good work, for the 
community usually gets just what it pays for. 

The author has heard public officials say that they figured to 
catch a sucker at every letting. They often did, but the result 
was that they either got a rotten job or had the difficulty of 
finishing the work themselves with all the usual compHcations. 
Fortunately this attitude has few supporters today and it may be 
stated as a general principle that uncertainty must be eliminated 



24 LOCATIOX, GRADING AXD DRAINAGE OF HIGHWAYS 

as far as possible, reasonable 'prices must be paid and the size of 
contracts should be varied in order to interest organizations that 
can best handle the road in question. 

The uniform use of long mileage contracts is no more desirable 
than the use of short contracts. Large organizations have a 
high overhead and equipment charge and there are generally net 
enough of them to insure hvely competition. They can afford 
to proA^ide labor sa^dng machinery'- which is a distinct advantage 
during times of labor shortage. The award of long contracts to 
large organizations is probably desirable for high priced rigid 
pavements, particularly in sparsely settled communities. 

Short contracts tend to encourage competition. Thej' can 
generally be finished in one working season which eliminates 
considerable uncertainty in the labor situation and the cost of 
materials. The}' can generally be liandled with local labor, par- 
tic idarly in well settled districts; they cause less inconvenience 
to the traveUing pubhc during construction. They are probably 
desirable for the construction of roads in well settled districts, 
particularly where the macadam form of pavement is used. 

Uncertainty in bids can be reduced by complete and definite 
plans and specifications that have the reputation of being en- 
forced. By definite statements of the requirements of materials 
and the location of acceptable supphes of these materials. By 
the pubhcation of the engineer's estimate of cost with a state- 
ment as to the maximum bid that will be considered in award- 
ing the contract and by the pro^dsion that in case a responsible 
contractor makes the low bid under the hmit stated and no award 
is made that he vr\\\ receive a reasonable fee for making the bid. 

To determine reasonable prices every large state organiza- 
tion can afford to develop a construction department which can 
do certain jobs each year to gauge reasonable construction costs 
and to take over for completion any contracts that may be can- 
celled for non performance. 

Maintenance. — The final cost and length of life of pavement 
surfaces depend on the efficiency of maintenance. Mainte- 
nance is the most disagreeable featm^e of road programs. It 
is well to remember that the only permanent feature of road work 
is Repair and that no pavement will last long no matter what 
its original cost. Maintenance is something that we have 
always with us, that is the fly in the ointment, that makes the 
Highway Commissioner grayheaded if he is inclined to worry 



ECONOMIC HIGHWAY DESIGN 25 

and that in many cases has not been handled with much fore- 
sight by the legislative bodies responsible for maintenance 
appropriations. 

Efficient maintenance can only be accomplished by preventing 
damage instead of repairing damage and it is very difficult to per- 
suade a non technical legislative body that large sums of money 
are necessary for this work before they have some physical evi- 
dence of the necessity. Such evidence is only supplied by a road 
that has been allowed to go to pieces and that the public is com- 
plaining about. This involves reconstruction which is not prop- 
erly classed as maintenance and is much more expensive than 
preventive measures. 

Maintenance policy is an excellent example of the fact that 
the future has a habit of taking care of itself. In the author's 
home state, New York, no adequate maintenance policy was 
adopted at the start of State aid road construction. In a short 
time the necessities of the situation gave the necessary impetus 
for some improvement in maintenance work and this improve- 
ment has been steady. In the last eight years (1913-1920) the 
organization has reached a stage where it has demonstrated its 
abihty to handle all kinds of pavement repair with moderately 
good results provided the necessary yearly appropriations are 
made. Such appropriations are not yet up to the requirements 
of really farsighted efficient maintenance but we hope it is only 
a question of time until this is also accomplished. This gradual 
development of efficiency is very typical of the average com- 
munity. Reasonably effective maintenance has been accomplished 
and can be accomplished in spite of the practical difficulties of 
the job. 

The comparative cost of flexible and rigid pavement main- 
tenance will be discussed in detail in the second book of this series 
but at this point it is sufficient to note that under poor maintenance 
flexible gravel or macadam construction is worthless ; that under 
moderately effective maintenance they compare favorably with 
rigid pavements in ultimate cost on local service roads where all 
classes of road material are locally available and that under really 
good maintenance macadam has a distinct advantage over rigid 
pavements up to about 1800 vehicles per ten hour day in the busy 
season. It is well not to permit the fear of inadequate main- 
tenance in the immediate future to influence the selection of 
pavement type. 



26 LOCATIOX, GRADING AXD DRAIXAGE OF HIGHWAYS 

The fact that maintenance has been poorly handled in some 
cases, resulting in a short life of the macadam pavements has 
led a number of Engineers to dodge the difficulty by building rigid 
pavements. As a matter of fact the slogan of the concrete men, 
the brick men. etc., "Build the maintenance into the road'' has 
considerable merit pro^dded we admit that the American Pubhc 
Official can not handle maintenance. 

The man in charge of maintenance has a hard job. His 
work is not spectacular. If he keeps the roads in excellent condi- 
tion it is taken as a matter of course. If the roads are not kept 
in good shape very httle charity is extended in his direction even 
though he has been hancUcapped by a shortage of funds. Legis- 
lators as a rule do not appreciate the large amoimt of money re- 
quired and apparently take dehght in cutting the estimates 
where they would not think of tampering -^dth construction ap- 
propriations. Maintenance is a convenient way of dispensing 
minor patronage, etc., but good work has been done and can be 
done and if the community ever expects to complete a general 
system of roads it must be done. 

There is one thing certain, the pohcy of " building the main- 
tenance into the road'^ by the use of a short mileage of extremely 
liigh priced paA^ements on accotmt of the fear that it will be im- 
possible to maintain a less expensive type ^dolates the first prin- 
ciple of Mileage Service. It also often puts the hidden burden 
of maintenance on the community at large as part of the original 
construction cost instead of on the road user as a yearly charge. 
This last contingency has been avoided in some cases by finan- 
cing original construction with auto Hcense fees but the wisdom 
of this method is open to argument where this robs needed main- 
tenance funds and the short mileage result can not be overcome. 
Needlessly short mileage is the most serious criticism that can 
be made of any general pohcy deahng with an incomplete Road 
System. 

The last principle of design becomes: efficient maintenance is 
essential. The lack of a well defined maintenance policy should 
he remedied by maMng the maintenance effective and not by side- 
stepping the issue with a needlessly short mileage of high first cost, 
low maintenance cost pavements. 

Summary of General Principles. — The foregoing principles 
mav be summarized as foUows: 



ECONOMIC HIGHWAY DESIGN 27 

First. — The construction of the greatest possible mileage of connected 
roads of a type suitable to the stage of development of the community and 
its existing traffic. Mileage is the first and foremost factor of service. 

Second. — Traffic must be regulated not only to save past investment but 
also to enable the community to finance any enduring general system of 
roads and to make economic engineering design possible. 

Third. — ^Local traffic is entitled to first consideration in the location of 
roads and their design except for a comparatively small mileage of special 
service roads. 

Fourth. — The maximum regulated load for the class of service for which 
the road is intended should govern the strength of the pavement founda- 
tion and bridges and no attempt should be made to reduce construction 
cost by using weak foundations. Heavy traffic must be ruled off from local 
service roads. 

Fifth. — The varying demands of traffic require variations in pavement 
type. As a general rule avoid the use of rigid pavements on local service 
roads except for unusual conditions of material supply. 

Sixth. — ^The number of vehicles and the percentage of horse traffic using 
the road govern the width of pavement and its surfacing. 

Seventh. — Volume of traffic controls the designs of safeguards. On light 
traffic roads confine safeguards to warnings. On heavy traffic roads make 
the road as near fool proof as possible. 

Eighth. — Inferior material should never be used but the type of pave- 
ment should be varied to permit the proper use of existing local materials 
or the cheapest imported materials. 

Ninth. — Every effort should be made to obtain a reasonable term of bond 
but if a long term bond has been adopted do not permit the term of bond 
issue under which the improvement is made to influence the selection of 
pavement type. 

Tenth. — Uncertainty must be eliminated as far as possible in contract 
relations, reasonable prices must be paid to insure good work and the size 
of the contract should be varied in order to interest organizations that are 
best fitted to handle the roads in question. 

Eleventh. — Efficient maintenance is essential. The lack of a well de- 
fined maintenance policy should be remedied by making the maintenance 
effective and not by sidestepping the issue with a needlessly short mileage 
of high first cost, low maintenance cost pavements. 

Conclusion. — These principles will serve as a basis for the 
development of detail design practice. While they may not 
apply to all cases, some such general scheme that will fit the 
requirements of the locality in question is a necessary step in 
any reasonable scheme of design and construction. They serve 
as a fixed goal to aim at and are very useful as a guide when 
the Engineer is floundering in detail or badly hemmed in by 
circumstances. 



CHAPTER II 
PROPORTION AND ECONOMY IN DESIGN 

The Relative Importance of the Detail Elements of Design. — 

^lost roadwork can be classed as a step in progi'essive improve- 
ment; the highway is gradually bettered from a trail to a high- 
class, modern, hea^^'-traffic thoroughfare as its use or prospective 
use waiTants the expenditure. In the majority of cases the 
money at hand is not sufficient for the complete construction of 




Fig. 10, — Expensive rigid pavement highway with dangerous alignment, dan- 
serous section, fiimsv guard rail and weak bridsrina. 



all the features that are desirable even at the time when the im- 
provement is made, and it is never sufficient to build a road that 
wiU completely fill the requirements of the future. Some fea- 
tiu-es have to be omitted or shghted. It therefore seems well 
worth while to encourage first the construction of reasonably 
good ftmdamental elements which act as a basis for the final 
improvement, and then in logical order as many of the other 
desirable parts as can be built. 

"Where the ftinds are inadequate for a completely satisfactoiy 
design the results often show a lack of proportion. Figiue 10 

2S 



' PROPORTION AND ECONOMY IN DESIGN 29 

will perhaps show in a general way the point I have in mind. 
It shows a high-class pavement with dangerous alignment, dan- 
gerous section, flimsy guard rail and weak bridging. 

It certainly pays to construct what is done so that it can 
be readily strengthened and widened as the future requires, 
without losing the benefit of previous work. The following 
tentative Ust illustrates an order of importance of design ele- 
ments which probably applies to most cases, with some minor 
variations : 









te_ 4 




■^^X 




^M 








^^BM^a^JK 




1 




fll^H 








lld^MiK^ 


»_i^" jgsJSa 


i^B 


^^^mn 


^^^^^^H 








JP^- 




_ — 




^^^^H 






^^^^^^^^ 








"^ 


^9H|^H 




M 




,. « 










1^ 


wm 




» .. 








^^ 



Fig. 11. — Substantial modern bridge with well designed approach protected 

with concrete guard rail. 

DESIGN FEATURES 

First, selection of the best general route. 

(a) Best location for the development of the territory. 

(6) Longest open season. 

(c) Least rise and fall. 

{d) Length and cost. 
Second, selection of the most natural engineering location following the 
desired general route 

(a) Reasonable grades. 

(6) Exposure. Avoid north exposure and areas of deep snow. 

(c) Character of excavation. Avoid rock, slides, etc. 

{d) Drainage problems. Avoid flood areas, stream crossings, etc. 

(e) Avoid artificial restrictions such as section line locations, etc. 
Third, detail requirements of design. 

(a) Reasonable maximum grade, considering future requirements. 

(fc) Economical intermediate grades. 



30 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

(c) Safe and economical alignment, considering future requirements. 

(d) Width of roadway safe for traffic, eliminating dangerous ditches. 

(e) Width of roadway convenient for traffic. 

(/) Sufficient culverts and bridges to protect the roadway, considering 
the future. 

(g) Permanent construction of these culverts and bridges. 

(h) Sufficient width of clearing for sun to reach road. 

(i) Safety provisions. Protection for traffic at dangerous places. 

(j) Provision of liberal width of right-of-way, considering future widen- 
ings and development. 
Fourth, improvement of the road surface. 

(a) By selective soil treatment. 

(6) By gravel, chert, macadam, etc. 

(c) By rigid pavements. 
Fifth, improvements for the future. 

(a) A higher-grade surface. 

(fc) A wider hard surface. 

(c) Provision of sidewalks for pedestrians. 

(d) Planting trees, etc. 

An examination of the roads in almost any locality leaves the 
impression that a Uttle more emphasis on and attention to the 
better construction of the fundamental features will add to the 
reasonable proportion of design and be a move in the right 
direction. 

The following typical cases illustrate the usual problems that 
occur and indicate their general solution. 

General Solutions Pioneer Districts. — Where no road exists 
and the funds are entirely too small for good construction, a 
sufficiently cheap design is used to complete the entire length. 
Under these conditions the only requirement that must be met 
is the proper selection of general route, although it is probable 
that for the greater part of the distance the final engineering 
location can be followed. Considerable work of this kind has 
been done in the southwestern states, and the solutions are in- 
genious. Satisfactory wagon and automobile trails have been 
constructed under favorable conditions for as low as $20.00 per 
mile, while in difficult locations advantage has been taken of all 
possible expedients to keep the cost down. 

Where a poor but usable road exists between the terminal 
points, or for a portion of the distance, either the uncompleted or 
worst sections of the route are first considered. Under such 
circumstances the funds are generally sufficient to permit a 
moderately good engineering design, which must prvoide for a 
reasonably good grade and drainage scheme on the improved 



PROPORTION AND ECONOMY IN DESIGN 31 

sections, although the drainage structures may be cheap and 
temporary and the roadway narrow. 

Where a fair road has been previously built over the entire 
route, no improvement should be attempted unless it provides 
for a first class engineering design of grades, alignment, section 
and permanent drainage structures. 

Where a first-class natural soil road is in use the next step in 
progressive improvement requires either selected soil, gravel or 
hard surfaced construction of the traveled way. 

General Solutions Well Settled Districts. — The application of 
the order of importance of design elements for hard surfaced 
pavement work can be shown by three cases: 

Under the most favorable conditions in rich communities, the 
improvement is considered final and its design is based on an 
effort to obtain the most useful, and in the end the most economi- 
cal form of construction regardless of first cost. In this case all 
the engineering requirements may be fulfilled. 

In many communities, however, the funds are only sufficient 
to build a moderately good pavement, which will have to be 
bettered by reconstruction in a few years, to meet the increasing 
demands of the traffic. An improvement of this kind should be 
permanently and completely designed for proper grades, align- 
ment, section, drainage and safety provisions, up to a certain rea- 
sonable hmit and the balance of the money spent on the best 
type of hard surface that can be afforded. 

The third case is reconstruction, which usually confines the 
problem to consideration of the most suitable type of resurfacing, 
utihzing previous work to the best advantage. It also sometimes 
involves improved relocation. 

Reasonable Economy in Design. — The mileage to be con- 
structed is so great (see Table I) and the amount of money 
involved so impressive that it seems desirable to use all reasonable 
care to produce as many miles of road as possible with the avail- 
able funds. During the years 1913-1920 the author has made 
a careful review of some 2000 miles of road plans from different 
sections of the country with the idea of forming a reasonable con- 
clusion as to the trend of highway design and to see how closely 
current practice follows the well recognized principles of high- 
way engineering. The results of the analysis of these plans were, 
roughly, as follows: About 25 per cent, could be classed as first- 
class designs from an economical standpoint. Practically all 



32 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



Table. 1, — Road Mileage in the United States in 1914. (Bulletin 

U. S. Public Roads) 



State 



Total 

road 

mileage 



Miles 


Per- 


Total 


mileage 






sur- 


centage 


Per 


Per 


faced 


surfaced 


sq. 


1000 






mile 


rural 






of 


popula- 






area 


tion 



Surfaced mileage 



Per 

sq. mile 
of area 



Per 
1000 
rural 
popula- 
tion 



Alabama 


55,446 
]2,075 
50,743 
61,039 
39,780 
14,061 

3,674 
17,995 
80,669 
24,396 
95,647 
73,347 
104,074 
111,052 
57,916 
24,563 
23,537 
16,459 
18,681 
74,190 
93,517 
45,779 
96,041 
39,204 
80,272 
12,182 
14,020 
14,817 
11,873 
79,398 
50,758 
68,796 
86,354 
107,916 
36,819 
91,555 

2,170 

42,226 

96,306 

46,050 

128,960 

8,810 
14,249 
53,388 
42,428 
32,024 
75,707 
14,797 


4,988 

253 

1,097 

10,279 

1,193 

2,975 

243 

2,830 

12,342 

679 

11,606 

30,962 

614 

1,148 

12,403 

2,067 

2,762 

2,489 

8,505 

7,828 

3,967 

2,133 

6,712 

609 

■ 1,204 

262 

1,659 

5,897 

261 

15,635 

6,003 

955 

30,569 

121 

4,726 

9,982 

693 

3,270 

363 

8,102 

10,526 

1,153 

1,442 

3,909 

4,922 

1,064 

13,399 

468 


8.99 

2.09 

2.16 

16.84 

3.00 

21.16 

6.62 

15.72 

15.30 

2.78 

12.02 

42.20 

0.59 

1.03 

21.40 

8.42 

11.74 

15.10 

45.53 

10.55 

4.24 

4.66 

6.98 

1.55 

1.50 

2.14 

11.83 

39.80 

2.20 

19.60 

11.82 

1.38 

35.16 

0.11 

12.83 

10.90 

31.95 

7.74 

0.37 

17.59 

8.16 

13.09 

10.12 

7.32 

11.61 

3.30 

17.60 

3.10 


1.08 
0.11 
0.96 
0.39 
0.38 
2.92 
1.86 
0.33 
1.37 
0.29 
1.71 
2.03 
1.87 
1.35 
1.44 
0.54 
0.79 
1.65 
2.32 
1.29 
1.15 
0.98 
1.39 
0.27 
1.04 
0.11 
1.55 
1.97 
0.09 
1.66 
1.04 
0.98 
2.12 
1.55 
0.38 
2.22 
2.03 
1.38 
1.25 
1.10 
0.49 
0.11 
1.56 
1.32 
0.63 
1.33 
1.37 
0.15 


31.3 
85.5 
36.9 
67.2 

100.9 

122.3 
34.9 
33.6 
38.9 
95.4 
44.2 
47.1 
67.3 
92.7 
33.4 
21.1 
65.3 
25.8 
77.5 
50.0 
76.3 
28.8 
50.6 

161.5 
91.0 

177.8 
79.9 
23.5 
42.3 
41.2 
26.8 

138.8 
41.0 
80.7 

100.6 
30.2 

120.8 
32.7 

189.8 
26.4 
43.6 
43.9 
76.2 
33.7 
79.0 
32.3 
56.9 

147.9 


0.097 
0.002 
0.020 
0.066 
0.011 
0.617 
1.240 
0.052 
0.210 
0.008 
0.207 
0.858 
0.001 
0.014 
0.308 
0.050 
0.092 
0.250 
1.058 
0.136 
0.036 
0.046 
0.097 
0.004 
0.001 
0.002 
0.184 
0.784 
0.002 
0.328 
0.123 
0.013 
0.750 
0.002 
0.049 
0.220 
0.649 
0.107 
0.004 
0.194 
0.401 
0.014 
0.158 
0.097 
0.073 
0.044 
0.242 
0.005 


2 82 


Arizona 


1 79 


Arkansas 


80 


California 


11 32 


Colorado 


3 02 


Connecticut 


25 89 


Delaware 


2 32 


Florida 


5 29 


Georgia 


5 96 


Idaho 


2.65 


Illinois 


5.37 


Indiana 


19 88 


Iowa 


0.39 


Kansas 


0.96 


Kentucky 


7.15 


Louisiana 


1.78 


Maine 


7.65 


Maryland 


3.90 


Massachusetts 

Michigan 


35.29 
5.28 


Minnesota 


2.42 


Mississippi 


1.34 


Missouri 


3.54 


Montana 


2.51 


Nebraska 


1.36 


Nevada 


3.82 


New Hampshire 

New Jersey 


9.47 
9.40 


New Mexico 

New York 


0.93 
8.10 


North Caroliria 

North Dakota 

Ohio 


3.18 

1.86 

14.54 


Oklahoma 


0.09 


Oregon 


12.89 


Pennsylvania 

Rhode Island 

South Carolina 

South Dakota 

Tennessee 


3.29 
38.59 
2.53 
0.72 
4.64 


Texas 


3.56 


Utah 


5.76 


Vermont 


7.71 


Virginia 


2.46 


Washington 


9.17 


W est Virginia 

"Wisconsin 


1.07 
10.08 


Wyoming 


4.56 






United States 


2,445,760 


257,291 


10.52 


0.82 


49.5 


0.086 


5.21 



the designs showed minor wastes, but for the plans classed as 
good, revisions would not result in any practical advantage. 
About 75 per cent, of the plans showed a material expenditure 
of money for which no adequate return was obtained, amounting 
to from 5 to 20 per cent, of the cost. On some of the roads which, 
as built, served the traffic well, this excess might better have been 
spent on other jobs. On some of the roads which, as built, were 



PROPORTION AND ECONOMY IN DESIGN 33 

not up to the requirements of the traffic, the waste might better 
have been apphed to their own improvement in fundamental 
features. 

The general faults most noticeable were: 

Too much spent on the reduction of intermediate grades. 

Too much spent to obtain long straight grades. 

Too much spent on sections with deep ditches. 

Not enough spent on reahgnment at dangerous locations. 

Not enough spent on relocations necessary to get reasonable maximum 
grades. 

Not enough spent on long-span bridges. 

Too much spent on width of macadam. \ 

Not enough spent on depth of macadam. 

Too much spent on imported materials where local materials were avail- 
able in limited quantities. 

One of the objects of these books is to discuss in detail various 
proved means of effecting economies without reducing the use- 
fulness of the roads. At this point, however, it is not necessary 
to more than indicate the different parts of design that are par- 
ticularly susceptible to such saving. 

Systematic grading design will often reduce the work from 500 
to 2500 yd. per mile, amounting in money, on an average, to 
from $500 to $1000 per mile. The proper use of local material 
particularly in foundations is a large factor in economy and will 
often reduce the cost from $1000 to $3000 per mile. Reasonable 
variations in pavement width and in the thickness of surfacing 
courses is effective and in many cases saves from $1000 to $2000 
per mile. A very conservative estimate of savings due to these 
systematic minor alterations is from $1000 to $2000 per mile. 
These savings are not spectacular for any one job but if consis- 
tently used their advantage on any large program is very evi- 
dent. They will more than pay for all the necessary engineering 
work in connection with the entire program. The small addi- 
tional work required for a careful analysis is the best pos- 
ible engineering investment for the community that can be 
made. 

Tests of Designs. — It is certainly well worth while to test out 
each finished design to see if it complies with the general princi- 
ples which have been discussed and also with the detail economies 
that will be taken up later. The following list of questions in- 
dicate in a general way the points to be considered: 

3 



34 LOCATION, GRADING AND DRAINAGE OF HIGHWAY^ 

Questionnaire 

Is the alignment suitable for all reasonable requirements of the future? 

Is the ruling grade suitable for all reasonable requirements of the future? 

Is the section, ditch to ditch, safe and suitable for present traffic? 

Is the right-of-way wide enough for future requirements? 

Are there ample culverts for all requirements of the future? 

Are the culverts proportioned properly as to size considering run-off? 

Are the culverts long enough to be safe and large enough to maintain? 

Are the bridge superstructures strong enough for present traffic? 

Have all permanent culverts and bridges been designed strong enough 
and wide enough for, say, 50 years? 

Are the bridge abutments for new temporary superstructures solid enough 
for future permanent superstructures? 

Are the ditches road ditches and not farm drainage ditches? 

Are the safety provisions real safeguards or are they only warnings? 

Is the road surface thick enough to handle present traffic without founda- 
tion failure, considering the subsoil conditions? 

Is the road surface wide enough for present traffic ? 

Is the surface of the general type required by present traffic? 

So much for Proportion — now for Economy: 

Does the grade line conform with the principles of economical design? 

Do the sections fluctuate to conform to economical design? 

Has the selection of pavement type been based on the most economical 
use of local materials? 

Has the design been varied to use limited supplies of local material with 
short hauls? 

Is the width reasonable, and has it been varied on a road that has heavy 
traffic part of the distance and light traffic part of the way? 

Has the depth of macadam been varied to meet the different require- 
ments of the soils and kept to a reasonable minimum? 

Have the culverts and bridges been designed for the most economical 
type for the span in question? 

Have the types of culverts been varied to get the cheapest result, con- 
sidering local materials, in comparison with market quotations and cost of 
long hauls on imported materials? 

Are the specifications flexible enough to permit the reasonable use of 
local material? 

Does the testing laboratory make an effort to approve the reasonable 
use of local material, or is it inclined to hold arbitrarily to the highest stand- 
ards, regardless of the relative importance of the job in hand? 

The designer should, however, bear in mind that imperfections 
in construction and indeterminate factors make too close a 
theoretical design impracticable and that a certain factor of 
safety must be provided in all his plans for such possibilities. 
The application of this to the different elements of design will be 
discussed throughout the books. 



PROPORTION AND ECONOMY IN DESIGN 35 

Order of Work. — The detail methods employed in the field 
and office work are described in the third book of this series. 
In pioneer districts the general order of work is as follows: 

A preHminary investigation is made to determine the general 
route, the best engineering location and the approximate cost 
of construction. It forms the basis for the general scheme of 
financing and design. It is the most important feature of new 
road location, and if well done insures the completion of a rea- 
sonable program of construction with the funds at hand. It also 
prevents wasteful expenditure on ill considered or unsuitable 
location surveys and plans. The detail location survey based 
on the preliminary conclusions is next made to secure the data 
for the final office design, which carries out in detail the recom- 
mendations of the first report and completes the work prelimi- 
nary to construction. 

In well settled communities the order of work is the same. 

The character of the information for the preliminary inves- 
tigation is different, but the object is identical; namely, to pro- 
vide a basis for appropriations and reasonable design. The 
preliminary data deals largely with probable traffic, available local 
materials and the most suitable and economical pavement type. 
The location survey provides the essential data for design, using 
somewhat better methods than for mountains conditions, and 
the office work is more detailed and complete. 

Conclusion of Chapter. — During the last ten years, road de- 
sign has been improved by standardization. This is a necessary 
step in the development of efficient organizations but it is only 
a preHminary step which has already been carried up to or be- 
yond its desirable limit in many states. The more or less preva- 
lent stereotyped use of Standards not only results in a needless 
expenditure of public funds for construction but tends to dis- 
courage independent thinking by the rank and file of the force. 
Standards serve their purpose by providing a minimum standard 
of excellence and by saving time and duphcation of effort in 
designing ordinary structures; that is about their limit of use- 
fulness. Further improvement in general highway practice 
lies very largely in an educational policy along the lines of system- 
atic economical design and the use of engineering judgment in 
the application of standards. 

The natural tendency of the man new to roadwork is to copy ex- 
isting local practice with very little thought as to its reasonable 



36 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

application. If designers will think for themselves a long step 
forward is accomplished. They are not so apt to be stampeded 
by trade propaganda or to develop a habit of mental laziness 
that is wilhng to accept any method that will, to use a slang 
phrase, '^Get hyJ^ Any technical analysis is of value only when 
its appHcation is based on common sense. It is very evident 
that any system of design which does not take advantage of 
and encourage the initiative of the intelhgent and experienced 
men on the force is radically wrong. It is probably true that a 
few of the usual Civil Service Engineers and Inspectors are not 
active mentally. For this class of men an effective way to 
encourage reasonable design and force the designer to make an 
analysis which he can defend is by ^^ Check Lists J'' This method 
is illustrated in detail in the third book of this series. However, 
it is just as well to emphasize the fact that there is a genuine 
personal enjoyment in a complete, reasonable, economic analysis 
of road design. A great many young men have said that it 
took them a long time to realize this and that they were as a 
rule indebted to some older Engineer for the point of view. I 
have seen the radically different results obtained by these men 
after they had developed the habit of analysis and it is hoped 
that the economic advantages of careful engineering can be 
effectively shown throughout the books and particularly in 
Volume III by examples of actual design worked out in the 
usual standard manner and then modified by systematic criticism. 
The success of any program depends very largelj^ on the per- 
sonnel of the directing organization. The national tendency of 
making public work the football of partisan politics may add 
interest to life but it certainly does not add efficiency to a road 
program. It is often extremely difficult to carry out any well 
balanced plan. We generally get the roads somehow and some 
way but main strength and awkwardness play a large part in 
the game. It is well to bear in mind that while present procedure 
can undoubtedly be improved that the net result of Highway 
programs to date has been excellent and. the communities have 
received entirely satisfactory returns on their investment in im- 
proved roads. State and Federal control has radically improved 
engineering design and methods of financing. It has eliminated 
most of the pettj^ local interference with sound design but the 
danger to guard against from centralizing the authority lies in 
too much generalization, lack of flexibility and the beaurocratic 



PROPORTION AND ECONOMY IN DESIGN 37 

attitude which tends to smother the development of the promising 
younger men. Any method which tends to stabiHze general 
policy or improves the character of the engineering organization 
is a move in the right direction. Careful layouts and complete 
classifications which are well made and well advertised have some 
effect in preventing radical changes by successive administrations. 
These expedients are discussed in the next chapter. 



CHAPTER III 

CLASSIFICATION, ROUTE AND GENERAL ENGINEERING 

LOCATION 

Road Systems. — The first step of road improvement programs 
is to plan the system and classify the roads. A general layout 
is necessary to insure a well connected and serviceable system 
for both local and long distance traffic. A great deal of thought 
has been given to the layout of state and county highways 
and the general plans are fairly well fixed in most locahties. 
Comparatively few engineers will have the opportunity to assist 
in planning large systems but it will do no harm to give a short 
discussion of the general principles governing layout, classifica- 
tion and the selection of route. 

Layout of Systems. — ^Layouts are based on the part that the 
highways play in the general transportation scheme for the 
locality in question. From the standpoint of heavy hauling, 
highway systems generally act as short feeders for railroad 
freighting. This has been somewhat modified by motor truck 
development, as discussed later, but as far as long-distance 
hauling is concerned highways as a rule are not a large factor. 
However, long-distance freight hauling becomes a deciding 
factor for special districts removed from railroad facilities or 
for metropolitan districts with closely located cities. Light 
vehicles have a greater range of action and are not as closely 
confined to definite routes. Local topography modifies the 
various schemes but the traffic requirements usually result 
in a system of main roads radiating from shipping points, cities, 
county seats, etc., connected at proper intervals by cross roads. 
Each local system is tied to the adjacent system by a reason- 
ably direct route. (See Fig. 13, Western New York State 
& County System.) (See Fig. 14, for Local System Monroe 
County.) The advantages of a complete plan of this nature is 
very evident. Single bond issues or appropriations are rarely 
comprehensive enough to complete even a skeleton system of 
roads for large areas but if a more or less complete system of 

38 



GENERAL ENGINEERING LOCATION 



39 



Hdmmood 

i 






Crown Po/nfQ 



Vd/pardiiO^ 



m/idr^ 1 I ! 



f / 



Orchard <7/^yfi I 



b/TnoA 



f^^rjdn 



/fudurn 
Win3mac\ I \ 1 'J ■ _^ j 






i5^ ; l\ 



\ 



Delphi ! 



M//iar 



'^/'^^^o^' i i 

'' J: ' 



/f^ns^r 



*/./i;f f 






Franf(/o)r^ 



^HoMomd^ \ I 

„.. i I 7^/)i)rd 

Y/iJtdndr/^ ,.\ 1 ^ 



y///(>\ 



.. "I v' i V.-i.4 

^eit/porf^ I 






jpp^ 



l/557< 



^derjo/7 



Penh/efon 



tt^h, 



f'^'Vjvi 



'^'J'/Ti 



V>J 



'<:Vi» 



^/^ 



//jIj 



>i7/79 ^/■<?<°/7(r<^J/^( 



P/o,n//ela 



v 



'T 






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L._._V-| 

-I I \ ' 



C^n/Af"^ 



I 






\Broof(y/i^ 



Wreen^urg 



y 



nOO<^ 



I 



Y ^'>^oo^^o \ \ '' Brecon,- jr?^^;^:::^'^on I /.'-■■' 



YZm/ScV7 ' 



, ^cv -I- , ^'-omL 



Harmony 



_yrr»^ 



ycifbnieT 



Mf" 



FrcdelicJfs- 



fMf\ 









Tro\ 



oy 



Port 



Fig. 12. — Indiana state road system. (Skeleton through routes.) 



40 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

roads is laid out at the time the improvement program is started 
it is possible to see at a glance the part each road plays in the 
general scheme. This makes it easier to design individual roads 
to fit into the finished system, and it is also easier to decide on 
a reasonable order of construction. 

Systems are laid out by careful study of maps, field inspections 
of alternate routes, conferences with local people and sometimes 
are affected by traffic estimates on rival roads. The value of any 
proposed highway system can be roughly indicated by trafiic 
counts; to illustrate, the State of Ilhnois concluded from such 
counts that 15,000 miles of her roads out of a total of 95,000 
miles carried 90 per cent, of the total traffic. It should, however, 
be remembered that road improvements often change the move- 
ment of traffic and that existing traffic routes should not outweigh 
evident advantages of other locations. Such a count may not 
determine exactly which roads to improve, but it indicates that 
a well laid-out system containing 15,000 miles will probably give 
excellent service as a system of Main Roads. 

Complete State or National Road maps may weU be compiled 
showing the existing movement and volume of traffic (see page 
45); the condition of existing roads and bridges; the location 
of road materials; the location of industries affected by high- 
way haulage; the location and character of natural resources 
dependent on highways for their development. Such data 
aids reasonable layout and design. Preliminary data of this 
kind is rarely well worked out on account of the time and money 
required for careful study. The insistent demand for immediate 
construction regardless of where the dirt flies is responsible for 
many disappointing programs. 

Classification of Roads. — Highways are classified in two ways; 
to apportion funds and to determine pavement type. 

The classification as National, State, County or Town High- 
ways depends on their location and relative importance to the 
present or future transportation needs of the country. Such a 
classification not only furnishes a reasonable basis for the appor- 
tionment of funds but it also provides a shding scale cf excellence 
for the design of the fundamental featm^es of different classes of 
road improvements. 

This does not mean that because a road is designated 
as a State or National road that it is necessarily entitled to ex- 
pensive construction. Extensive State and National programs 



SUMMARY OF DATA 

ToM Road Mileage 6700 

}> Town Rocds .S3S0 

" Sifats and Coiinfy System.... I3S0 

OASSIFICATION STATE AMD COUHTY ROA0S 





Mil<?s 


<'/o5fateRds 


%Tokiimmie 


Class 1 


no 


13 


3 


Class 2A 


140 


10 


B 


Class 2 


600 


44 


9 


Class 3 


440 


33 


6 


Town Roads 


S3S0 




80 




MAP Of 
DIVISION N0.7 

DEPARTMENT OF HIGHWAYS 
STATE OF NEW YORK 

/ / Z 3 f f g 7 

ao o a Highmi/ilKirf^pieparedforkttmgorrecertfljsun/^ 
■■■■ Highways under conlract" 
Highwm/s as built' 



S Dl^'flastCdrrecfion * * * • Pi^P^S^ K'ffhwOj^ 
e May/^/Siff Town Roads 



DoK/n Clasiification 



Fig. 13. 



, COLOR SCHEME „ .,. ,. 

i^eci-,sWassf^-'„%i^ 
Green — Class eA j for 
Black — Class 2 1 Illustrative Purposes 
Ydlow—Classs) '^^o 



{Insert facing page 40) 



rOiOCKPORT 




SUMMARY OF DATA 

Total Road Mileage ^6700 

^ Town Roads. .5350 

" 5fats and County System.... 1350 

CLASSIFiarm STATE AMD COUHTY ROADS 



+*TD SOWUS POtKT 





Miles 


%5fafeFds. . %To^! Iftleam 1 


Class 1 


170 


13 


3 


Cass 2 A 


140 


to 


2 


Class 2 


600 


44 


9 


Class 3 


44-0 


33 


6 


Town Roads 


5350 




80 




GENERAL ENGINEERING LOCATION 41 

cover a wide range of construction from thickly settled districts to 
pioneer territory. The location and demands of existing traffic 
or the expected traffic in the near future control the desirable 
present expenditure on any road whether it is a town or national 
highway, but if the road is designated as a national route it is 
probable that in the future it will carry a large volume of traffic, 
and it indicates that the progressive stages of improvement 
may well provide liberally for right of way, alignment, grades, 
etc. 

Classification for Financing. — A complete layout and classi- 
fication scheme aids the proper apportionment of funds. The 
distribution of Federal, State and County aid to through routes 
and to local service roads is an extremely difficult problem from 
a practical standpoint but considering that about 90 per cent, 
of traffic is local, too much help or too much stress on the immedi- 
ate completion of a skeleton system of through routes is open to 
question unless such routes can be located and built to act as 
the main arteries of local traffic. Unless the local service pro- 
gram is fairly well completed, large amounts cannot be reasonably 
spent on high priced connecting links through sparsely settled 
outlying districts which have very little value except for tourist 
travel. If no line of communication exists a moderate priced 
road is a good investment but excessive expenditures are to be 
avoided. 

We have no system of National Highways as yet but in all 
probability it is only a matter of a short time before a start will 
be made. Federal Highway aid is an accomphshed fact. The 
present law (1920) requires State or State-County co-operation 
and is laid out apparently with the idea of improving general 
administrative conditions in road programs. The actual con- 
struction done under this act includes local service roads as well 
as through routes, which is a sound proposition. Work of this 
kind can, however, be well supplemented by a National Trunk 
Line System, provided the local service program is not pushed 
into the background by the more spectacular through lines. 

National Highways are naturally confined to the most im- 
portant interstate routes or special highways necessary for mili- 
tary purposes. Some very ambitious programs of mileage have 
been proposed but it is not likely that such a system will aggre- 
gate over 1 to 2 per cent, of the road mileage of the country. 
Such roads may well be constructed and maintained by Federal 



42 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

funds or by co-operation with the states under Federal supervision. 
The general principles of route selection later discussed govern 
the layout of these roads. 

State Routes cover the main inter-city routes or the main 
natural transportation or tourist routes. They do not as a rule 
include more than 4 to 6 per cent, of the total road mileage. 
They are usually financed by State funds or may receive Federal 
Aid. 

County roads include the main local service roads. They do 
not as a rule aggregate over 15 per cent, of the total road 
mileage. They are financed by county funds or may receive 
state or federal aid. 

While National, State and County roads do not probably 
include more than 15 to 25 per cent, of the total mileage in the 
country, they probably carry from 80 to 90 per cent, of the 
total traffic during some portion of its journey. 

Town roads constitute from 75 to 90 per cent, of mileage and 
while they are generally fight traffic roads they act as feeders 
for the main system and are of very great economic importance 
to the general transportation scheme. It is certainly extremely 
poor poficy to over-emphasize the value of the main roads and 
neglect the feeders. Expensive construction is not usually re- 
quired on such roads but they should be passable the year round 
and any comprehensive road scheme must deal liberally with 
these light traffic local roads. Town roads are financed by town 
funds and may receive county or state aid but rarely federal 
aid. 

Classification for Details of Construction Design. — The decision 
as to general type and width of pavement and section depends 
on the kind and volume of traffic expected in the near future. 
On any road the amount and class of traffic will fluctuate. 
The first improved roads in any locafity may for a time carry 
more than their share of the travel, which is naturally reduced 
by the subsequent construction of adjacent improvements, or it 
may be increased by the finking up of isolated improvements into 
a continuous route of improved roads between large centers of 
population. It can be readily seen that it is difficult to judge 
the amount of traffic a new road will have and that a short time 
traffic census is valueless as a basis for a definite conclusion. 
The general design is usually based on a comparison of the be- 
havior of different kinds of previously built roads that serve 



«<J 



-3V 



m 



m 




H S.JuDiON PEL. 



V.BlOOMFieLD -& 



LEGENO 

Town Macadam 

W///A Town Grai^<?l 

IHHB 5/0 fe and County Roadi 



CHARACTERISTICS OF MONROE CWNTY KOADS 
November lit ISIS 



ToM mikag? of highway i oulsidp of cily and villages 1^363.03 

tfileaye of Stale andState -County Highways complete ^ n ye 

'y////^ r -x ^ o I. A^ , . • Or under confracf ilO^eS 

iZ/^y^ City of Rochester boundaries offer Jan. Is. 1. 1916 Mileage of County Roads paid for by county and towns 5. 29 

/jgyr- Macadam Roads bui If- by towns 386. OO 

'Nvmbersonthismapare not lot numbers, ravel Rocd^ built by towns iV:, H 

but for the ready identification of any section of road 'otal mileage of improved roads 963.16 



GOOD R0AQ3 COMMITTEE 
WILLIAM C. PO/neRj Chairman 

DANieL HAimiNGTON 
HCHRY A. BOWMAN 

County Superintendent J.Y.McCLlNTOcn 



SeoKGe A.JOHNSOH 

CHARies e. voKB 



Fig. 14. 



(Iiiserl facing page 42) 



GENERAL ENGINEERING LOCATION 43 

districts similar to that under consideration and this can better be 
determined by a study of the locahty than by a locahzed traffic 
census. Roads on which high type macadams or rigid pavements 
are suitable may be divided into four general traffic classes. 

Class I. — Main trunk roads between large cities not over 100 
miles apart along natural transportation routes which accom- 
modate through truck freight traffic. Main radial roads for 
5 to 40 miles out of cities of say 50,000 and upward and in the 
business section of villages which carry the concentrated farm 
and truck traffic of a large area and are subjected to continuous 
heavy load travel. A Class I road usually carries more than 
2000 rigs per day in the busy season. 

Class II. — Main through automobile routes at greater dis- 
tances from the cities, which have a large touring car traffic and 
medium heavy farm traffic and some heavy trucking. A Class 

II road generally carries from 500 to 2000 rigs per day. 

Class III. — Secondary or feeder roads and cross roads having 
a medium heavy farm traffic and light pleasure travel. Class 

III also apphes to main roads in sparsely settled districts. 
Class IV. — -Pleasure or scenic roads that carry a large number 

of pleasure autos but fight steel tire traffic. 

Class I roads as a rule require rigid pavement construction 
while Classes 2, 3 and 4 are generally more economically served 
by thick modern bituminous or waterbound macadam (oiled) 
or gravel construction. 

Value and Limitations of Traffic Census. — Complete traffic 
counts taken at regular intervals provide definite data concerning 
volume and character of traffic and the direction of its movement. 
Such a census has an indisputable value in indicating the general 
character of our highway traffic. Even the usual short time 
census has some value in determining the general character of 
the traffic. The usual short time census however has a very 
limited value in connection with definite decisions of design. 

As far as design is concerned a well taken census can be given 
some weight when apphed to a road system before an improve- 
ment program is started. It has a very decided value for use 
in reconstruction programs where the improved system has been 
completed and traffic routes established. It has practically no 
value for a partially completed system where traffic may go out 
of the way to use the first improved roads. Any traffic census 
should be fairly complete and represent the seasonal variations 



44 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

of traffic. Detail methods are described in the second book of 
this series. 

Take a concrete example to illustrate the discussion. (See 
Traffic Map, page 45) . 

This map apphes to the partially completed state aid road 
system shown in Fig. 13, page 41. It was devised by Mr. 
Percy Waller of Rochester, N. Y. for use on Division No. 7 and is 
a much better method of summarizing the census than the usual 
tabular form. This particular map represents total volume of 
traffic. Similar maps can be prepared to indicate tonnage, 
or truck traffic, etc. It is a very effective way of showing the 
relative use of the roads and the distribution of travel at 
junction points. It is a valuable guide provided the data on 
which it is based is complete. 

This particular map however was based on the usual New 
York State short time census taken for two days (Aug. 14th 
and 15th, 1920) from 7 A. M. to 7 P. M. On account of the lim- 
ited scope of the data the census or any other similar census 
must be used with caution. Suppose . we analyze the data. 

The estimate does not show seasonal variation in classes of 
traffic (horse and motor). 

It does not give a reasonable basis for total traffic considering 
seasonal variation and night travel. 

It has some value in representing the relative traffic on the roads 
during the summer season but falls down in numerous instances 
on account of summer resort travel, special fairs. Dollar day at 
Batavia, special picnics and the fact that some of the shorter main 
line roads are not yet completed. That is, this census is not in 
itself complete enough to have much value and the road system 
is not near enough completed to give the probable traffic move- 
ment in some cases. If we had a 24-hour count for Monday in 
January, Tuesday in February, etc., we could eliminate much of 
the uncertainty provided the system was completed and the 
count was to be used in deciding on pavement types for 
reconstruction. 

Suppose we cite a few cases where the traffic figures would 
be misleading unless modified by a common sense study of the 
territory. 

In the first place the census was taken in the height of the auto 
touring season. It over-emphasizes the traffic on the through 
routes as compared with the secondary lines. 



GENERAL ENGINEERING LOCATION 



45 




46 LOCATIOX, GRADIXG AXD DRAIXAGE OF HIGHWAYS 

A census taken in the winter, fall or spring months would 
probably show a larger percentage of horse traflB.c particularly 
on the local service roads. 

The roads marked 5 are simimer resort roads and a seasonal 
census would change the volume radically. The roads marked 
P where affected by large picnics or county fairs. Batavia had 
a dollar day sale, Caledonia had a fair and all the farmers flocked 
to town The roads were unusually crowded. 

The road marked A will in the future be reheved by the com- 
pletion of the road marked B which will radically change the 
volume on these roads. 

On one imimportant road the local people asked a friend of 
mine to drive up and down as many times as he could to swell 
the coimt and said they were all doing it in order to help get a 
concrete resiul'acing job on that road. , 

One or two of the roads are in such bad shape from a lack of 
maintenance funds that the traffic count was less than normal. 

These points are mentioned to illustrate the statement that 
the most rehable basis for design of a road in a new or incomplete 
road program is a common sense study of the territory. A com- 
mon sense study, however, includes a well-taken traffic census; 
not the usual incomplete coimt. 

Example of Classification by Location and Census Combined. — 
A concrete example of a design classffication by location and 
census is shown in Fig. 13 and explained as follows: Its value as 
a basis for a continuous pohcy is seK e^adent. This particular 
territory is selected to illustrate the discussion as its problem 
is t^-pical of the usual road conditions. It illustrates a wide 
range of conditions and with sHght modifications will apply to 
most of the States. By means of a definite illustration we hope 
to strengthen the discussion of general principles. 

The roads shown in red are class one, entitled to strong rigid 
pavement construction or reconstruction. 

The roads shown in green are in the doubtful class designated 
2A. The use of rigid pavements or high-class macadam depends 
largely on the relative cost for each road. Any reconstruction 
should pro^i'de for a low maintenance cost siui'ace although the 
existing macadam base may be utilized if firm and sohd. 

The roads shown in black are class two, served most economi- 
cally, in most instances, by a thick modern bituminous macadam, 
with reconstruction of the same type. 



GENERAL ENGINEERING LOCATION 



47 



The roads shown in yellow are class three, on which the usual 
well-built modern waterbound macadam, maintained by surface 
oihng, will serve satisfactorily. The roads shown in green, 
black or yellow with red dots mean that a rigid pavement is 
desirable on account of water flooding and not on account of 
traffic action. 

Such a classification should be carefully made utilizing the 
best judgment of the entire engineering force and local authorities. 
It should be reviewed and co-ordinated by the chief engineer. 
If well made and given enough pubhcity it tends to stabilize 
the general construction and reconstruction programs as any 
new administration would hesitate to change it radically unless 
they could make an excellent argument for so doing. One of 
the most troublesome difficulties that the highway engineer has 
to contend with is the constant change of general policy inaug- 
urated by successive admim'strations and any method which 
tends to minimize such changes is a move in the right 
direction. 

The tentative classification shown in Fig. 13 was made by the 
author with the help of five other engineers, some of the mainte- 
nence men and local officials. It was prepared to illustrate this 
manuscript. It is not an official classification. General plans 
of this nature are not yet in ordinary use but it is only a question 
of a short time before they probably will be. 

In order to give an idea of the percentage of the different 
classes of road in the district shown, the following tabulation is 
inserted. 



Road classification 



Approx. percentage 

of state and county 

system, approx. total 

1350 miles 



Approx. percentage 

of total road mileage, 

approx. total 6700 miles 



Class 1 

Class 2A. . . 

Class 2 

Class 3 

Town roads 




3 

2 

9 

6 

80 



In order to show the range in classification for different terri- 
tories the following tabulation shows Wyoming county (a poor 
district) and Monroe county [a, rich thickly settled county). 



48 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Wyoming County 



Road classification 



Approx. per cent, of 
state and county sys- 
tem, approx. total 
mileage 175 



Approx. per cent. 

total road mileage, 

approx. total mileage 

1076 



Class 1 


4 



42 

54 


1 


Class 2A 





Class 2 

Class 3 

Town roads 


7 

9 

83 



Monroe County 



Road classification 



Approx. per cent, of 
state and county sys- 
tem, approx. total 
miles 400 



Approx. per cent, of 

total road mileage, 

approx-total miles 1368 



Class 1 


12 
20 
42 
26 


4 


Class 2A 


6 


Class 2 

Class 3 

Town roads 


12 

8 
70 



The outstanding feature of this classification is the comparatively 
small mileage of roads requiring rigid pavements at this time 
(1920). 

The value of a classification of this kind for design, apportion- 
ment of funds and appropriation estimates is illustrated as 
follows : 

National Routes. — It is self evident that the natural location 
of a national route should follow along the New York Central 
Railroad via Corfu, Batavia, Bergen, Churchville, Rochester, 
Fairfort and east to Syracuse. Such a road is class 1 for the 
entire distance in this territory. (Fig 13, page 41). 

State Routes (Fig. 13). — The state roads as actually built or 
proposed aggregate approximately 370 miles. To illustrate the 
statement previously made that the designation of a road as a 
state route does not necessarily entitle it to expensive construc- 
tion, the tabulation below shows the approximate number of 
miles of such state routes under a reasonable classification. 



GENERAL ENGINEERING LOCATION 



49 





Approx. mileage 


Per cent, of total 


Class I 


90 

80 

160 

40 


24 


Class 2A 


22 


Class 2 


44 


Class 3 


10 



Comparison of Actual Construction with this Illustrative 
Classification (Fig. 13). — As a whole the actual construction de- 
signs are fairly reasonable for the various roads. We have some 
under-designed Class 1 roads and some over-designed Class 2A, 2 
and 3 roads. 

The main roads built between the years 1900 and 1912 would 
be classed today as under-designed. This is due to the re- 
markable increase in volume and weight of motor traffic. The 
secondary roads of this period are satisfactory even today. The 
increase in traffic, the change in its character and a lack of ade- 
quate yearly maintenance funds, resulted disastrously in some 
cases which caused a swing in sentiment to very expensive pave- 
ments even on Class 2 and 3 roads. For the last few years there 
is too much tendency to spend excessive sums on Class 2 and 3 
roads. Class 1 roads are not over-designed and are in fact still 
under-designed. The more or less prevalent tendency to build 
$40,000 a mile roads on Class 2 and 3 highways tends to curtail 
needed mileage and is a very dangerous policy as it is liable to 
discredit State and National aid. We have been very much 
disturbed over too many cases of this kind and believe it well to 
emphasize the danger of such design. 

Appropriation Estimates for Construction (Fig. 13). — By as- 
suming a reasonable maximum expenditure for each class of road 
and not exceeding it when the road is put under construction, 
appropriations will more nearly accomplish what they are ex- 
pected to do. The recent change in general price level has 
about doubled the cost of construction as compared to prewar 
conditions. This has caused a necessary curtailment of mileage 
for funds raised before the war but in a great many previous 
cases the lack of reasonable appropriation estimates resulted in 
failures to obtain anything like the mileage expected and has 
caused a great deal of dissatisfaction and in some cases dis- 
credited an improvement program. 

4 



50 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

For the district shown in Fig. 13 (1920 cost conditions) a 
tentative scale of costs per mile may be assumed as follows: 

Class 1 not to exceed $50,000 on an average. 
Class 2 A not to exceed $40,000 on an average. 
Class 2 not to exceed $30,000 on an average. 
Class 3 not to exceed $20,000 on an average. 

Main town macadam roads, $7000 to $10,000 on an average. 

On this basis the complete state and county system, 1350 miles 
(Fig. 13), would cost approximately $41,000,000 exclusive of in- 
terest. This would be a fairly heavy burden but is not unreason- 
able with proper State and Federal aid if the construction period 
was stretched out over a reasonable term of years (15 to 20) and 
the twenty-five year serial method of financing used. 

Funds for the original construction of such a system may well 
be raised largely by a general tax levy supplemented in some 
cases by vehicle taxes to help take care of the interest on the 
bonds. 

The tentative scale of prices is for a rich district. For the 
first stages of improvement programs in poorer districts a lower 
order of improvement must be adopted. This is discussed in 
more detail in the second book of the series. 

The following tabulations taken from the Highway Green 
Book of the American Auto Assoc, 1920, show the total cost 
and average yearly costs of serial bonds. 

Total Cost of Serial Bond. — Total cost of a $100,000 serial 
bond bearing 3, 4, 5 or 6 per cent, interest and maturing at 
different periods from 5 to 50 years. 



Term in years 


3 per cent. 


4 per cent. 


5 per cent. 


6 per cent. 


5 


$109,000 


$112,000 


$115,000 


$118,000 


10 


116,500 


122,000 


127,500 


133,000 


15 


124,000 


132,000 


140,000 


148,000 


20 


131,500 


142,000 


152,500 


163,000 


25 


139,000 


152,000 


165,000 


178,000 


30 


146,500 


162,000 


177,500 


193,000 


35 


154,000 


172,000 


190,000 


208,000 


40 


161,500 


182,000 


202,500 


223,000 


45 


169,000 


192,000 


215,000 


238,000 


50 


176,500 


202,000 


227,500 


253,000 



GENERAL ENGINEERING LOCATION 



51 



Average Annual Cost Serial Bond. — Average annual cost of a 
$100,000 serial bond bearing 3, 4, 5 or 6 per cent, interest and 
maturing at different periods from 5 to 50 years. 



Term in years 


3 per cent. 


4 per cent. 


5 per cent. 


6 per cent. 


5 


$21,800 


$22,400 


$23,000 


$23,600 


10 


11,650 


12,200 


12,750 


13,300 


15 


8,267 


8,800 


9,333 


9,866 


20 


6,575 


7,100 


7,625 


8,150 


25 


5,560 


6,080 


6,600 


7,120 


30 


4,883 


5,400 


5,917 


6,434 


35 


4,400 


4,914 


5,429 


5,943 


40 


4,037 


4,550 


5,063 


5,576 


45 


3,756 


4,267 


4,778 


5,289 


50 


3,530 


4,040 


4,550 


5,060 



For a more complete discussion of Highway Bonds. (See Ap- 
pendix A). 

Prevailing Rates, General Road Tax. — In 1920 a state wide 
road tax was levied in 22 states varying from }{o to 4 mills. 
The general county road tax by towns for Monroe County, 
1920 (this territory being used for illustrative discussion) varies 
from 2 to 5 mills and averages about 2J^ mills. 

Preliminary General Yearly Maintenance and Renewal Esti- 
mates (Fig. 13). — It is generally believed that the road user 
should pay a large proportion of money necessary for the upkeep 
of the highways. This includes maintenance and renewals as 
the pavements are worn out. A relatively small percentage of 
such funds may properly be raised from general tax funds but 
only a small percentage as the community at large have usually 
done their share by constructing the roads under a general tax 
levy.^ To approximate the probable yearly burden that wiU 
fall on such users and that will be collected by auto licenses 
or some form of direct vehicle tax we may assume the following 
values for a road system that has been completed long enough 
to require the normal maintenance and reconstruction necessary 
to prevent deterioration in its value. The cost of maintenance, 
renewals and length of life of pavements is discussed in detail in 
the second volume of this series. 

1 This is discussed in more detail in the second book of the series. 



52 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Class 1 roads Approximately $2500 per mile per year 

Class 2A roads Approximately $2200 per mile per year 

Class 2 roads Approximately $2000 per mile per year 

Class 3 roads Approximately $1500 per mile per year 

On this basis for the district shown in Fig. 13 we may expect 
eventually a yearly expenditure of approximately $2,600,000 for 
maintenance and renewals of the main roads. To raise any such 
amount the auto hcense fees will have to be materially increased 
or some other form of tax adopted. The increase necessary 
is not however beyond the bounds of reasonable taxation. 

The maintenance funds have never been adequate for this 
territory which results in excessive expenditures for reconstruc- 
tion at intervals. Maintenance must be put on a business 
basis. The usual maintenance programs are often far from 
reasonable. 

General Distribution of Tax Burden. — At a number of places 
in the text we have indicated the quite generally accepted prin- 
ciple of paying for the original construction of modern highways 
largely by general tax levy and for the maintenance and recon- 
struction of such highways largely by vehicle taxes. While 
this is believed to be essentially sound there is opposition and 
disagreement from different sources and it is perhaps just as 
well to summarize very briefly the basis for such a distribution 
of the improvement burden. 

A successful tax program is based roughly on three main 
points. 

First. — The final burden shall fall on each individual as nearly 
as possible in proportion to the direct and indirect benefit received. 

Second. — The direct tax shall be paid by the individuals receiving 
the immediate direct benefit if they are financially able. 

Third. — The tax must be levied on a definite source comparatively 
easy to assess and be collected from individuals having the ready 
money for payment. 

No tax scheme works out without minor injustice. Libraries 
have been written on the subject but for this particular problem 
of road improvement one point of view may be expressed roughly 
as follows. 

Real property, motor vehicles, tractor or horse vehicles are 
definite sources of taxation owned by individuals presumably 
with ready cash to pay any reasonable tax burden. 

Most of the immediate and direct benefit of improved highways 



GENERAL ENGINEERING LOCATION 53 

is received by the owners of vehicles operating on the roads. The 
adjacent property owners and a small part of the community at 
large get some immediate benefit even if they are not direct 
road users. 

Some of the final direct and indirect benefits of a modern 
highway system are as follows: 

The improvement of the social and economic conditions 
of rural life which tends to prevent an unhealthy loss of rural 
population and stabahzes the fundamental relation of local food 
supply to healthy city development. 

The development of the natural resources of sections de- 
pendent on highway transport. 

The increase in the scope and power of the transportation 
system of the country which is at present taxed to the limit. 

The cheapening of short haul transportation of food stuffs. 

The raise in rural land values. 

Added recreational possibiHties for the community at large. 

Mihtary value in time of war. 

A well constructed modern highway system promotes the 
general welfare of the entire nation and each individual whether 
a road user or not gets some direct or indirect benefit. The 
cities cannot get along without the country. An increase in 
prosperity of the rural districts increases the prosperity of the 
cities; an increase in the prosperity of one state has some effect 
on the prosperity of all the others. The nation can only develop 
on the principle that the prosperity of the country depends 
on the prosperity of even the new poor districts. This is the 
foundation for State and Federal Highway Aid. 

The inauguration of a highway system is a benefit to every 
individual in the community. While the road user gets most 
of the direct benefit, it is rarely feasible at this stage of the 
improvement to tax him directly for a large proportion of the 
cost of construction. That is, before improved highways are 
an accompUshed fact, the vehicles are fewer in number and 
operated by financially poorer individuals. The completion of a 
modern highway system increases the number and effectiveness 
of vehicles and adds to the abihty and wilhngness of the owners 
to assume a larger tax burden. It is therefore generally beheved 
that the original construction of such a modern system under a 
proper classification based on reasonable regulation of traffic should 
properly be paid for largely by a general real property tax levy 



54 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

which is eventually quite evenly distributed over the community 
by rents, etc. 

The cost of mamtenance and the renewal of pavements depends 
on the volume and kind of traffic. The largest share of the 
benefit of keeping a road continually in excellent shape goes to 
the vehicle owner. There are two general classes of traffic, 
pleasure traffic and business traffic. If a pleasure vehicle is 
taxed a fak amount to cover the damage it does to the road, 
this is a luxury tax borne by the owner. If a business vehicle is 
taxed a fair amount to make the highway seK supporting, the 
charge is added to the other operating costs which go into the 
price charged to the consumer and the pubhc at large foots the 
bill. The principle of a vehicle tax for maintenance and renewal 
apparently has a sound basis in fairness. The minor practical 
difficulties in connection with justly applying this principle are 
no more serious than those encountered in the appUcation of 
any other tax principle not essentially as sound so that any 
emphasis that may be placed on minor injustice of assessment 
has no real weight as an argument against the value of this basis 
for taxation. A large part of any possible injustice in its apph- 
cation can be reduced by a weU thought out graduated Hcense fee. 

It is certain that if maintenance and renewal were paid by 
general tax levy that the pleasure traffic would escape its fair 
luxury tax and the business traffic particularly hea\7' hauhng 
would have an unfair advantage in competition with other 
transportation methods which pay their own cost of track or 
waterway construction and maintenance. In 1919 the average 
motor vehicle Hcense fee in the U. S. was approximately S9.00 
and ranged from So. 00 per average motor vehicle to §20 per 
average motor vehicle. Horse drawn traffic paid no fees. It is 
very e^ddent, particularly in the States which have constructed 
a large mileage of modern roads, that the present (1920) hscense 
fees are an entirely inadequate share of the highway tax burden 
and that so far vehicle owners of aU kinds have escaped nearly 
scot free from their share of the burden. A moderate raise 
in hcense fees, not beyond the bounds of reason, gradually 
increasing as a road system grows will handle the situation 
satisfactorily. 

Pubhc road tolls are not feasible except for a few special cases 
as they restrict the free movement of traffic so that some form of 
graduated vehicle license seems the most reasonable form of tax 



GENERAL ENGINEERING LOCATION 55 

for a large part of the cost (say 80 per cent.) of the upkeep of 
highways. 

Order of Construction. — The order of construction of individual 
roads dovetails in with the problem of apportionment and is also 
a fruitful source of trouble. Considering the third principle of 
design, Local Service, probably the safest pohcy where all the roads 
are in poor shape is to start the improvements from well-defined 
shipping points, county seats, cities, etc., and gradually extend 
the mileage until adjacent districts come together producing the 
finished through routes. If some of the existing roads are fairly 
satisfactory for traffic it is often desirable to modify this method 
by selecting the poor sections of the main roads for first considera- 
tion which eliminates the worst features of the system at once 
and results in quicker general use of the roads. 

Selection of Route. — The selection of route depends on the 
purpose of the road, the topography between controlling points 
and the stage of development of the community. Each case is 
a special problem but there are certain fundamental facts worth 
considering. The basis of decision on general route rests on good 
common sense and is not entirely an engineering problem. The 
road must go where it will do the most good and it is up to the 
engineer to locate it in detail along the general route. The 
route location rests on reasonable answers to questions of the 
following nature: Where will the road do the most good to 
develop the natural resources of pioneer districts or how can we 
locate this route to serve the greatest number of people in well- 
settled communities or how can we build this scenic road to give 
the most pleasure? If an attempt is made to solve all these 
problems strictly on the basis of the shortest distance and the 
easiest grades between terminals we would be in hot water. Any 
satisfactory solution considers the broad engineering principles 
of short distances, reasonable grades and the smallest amount 
of rise and fall but the final decision does not always rest on 
close analytical ton mile cost hauling figures. To illustrate; 
recreational roads through national and state parks or forests 
are usually laid out to afford the most pleasure; grades and dis- 
tance are sacrificed to obtain vistas, bold outlooks, and to reach 
points of historical interest or summer resorts. The cost of 
operating a car on such roads has no bearing on its usefulness 
and a location based on a close analytical ton mile hauling cost 
would be merely ridiculous. Suppose we consider a national 



56 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

highway from New York to San Francisco. Some through tour- 
ing will occur but its volume is very light and the cost of addi- 
tional distance is not of any consequence to this class of traffic. 
More touring will go one-half or one-quarter of the way but even 
this is of no great factor in comparison with the short distance 
traffic on the route. To lay out any long route on the basis of 
the shortest distance and easiest grades between terminals for 
through traffic and to disregard passing through or close to the 
most cities and villages on the route is evidently poor poHcy. 
This illustration is exaggerated to bring out the principle of 
route selection in well-settled communities which is namely: 
To pass through the most populous areas, and either close to or 
through the most cities and villages that can he consiste7itly done 
without too much additional distance. This same principle applies 
to state and to purely local roads and may be summed up as 
direct contract with the greatest number of people. 

As the distance between controlhng points becomes less the 
factor of commercial hauhng has a larger bearing on the selection 
of route until we reach a point w^here the engineering require- 
ments of location govern the selection. That is, a reasonably 
low ton mile hauhng cost governs the short integral parts of any 
long route location. At the present time (1920) motor freight 
hauhng in competition with railroads is rarely economical for a 
distance of over 80 to 100 miles between terminals. This limit 
will probably fluctuate but it is not hkely to increase much and 
for the time being it does not seem desirable to permit the factor 
of long distance motor freight hauhng to influence the selection 
of route between large cities directly connected by rail over 100 
miles apart. Where large cities are located closer than this and 
there is a large volume of heavy motor hauling it is possibly 
better to save distance by omitting some of the local service. 
Where large cities are isolated heavy trucks rarely operate to 
outlying towns farther than 30 to 40 miles. Take a concrete 
instance to illustrate this principle (see Fig. 13, opposite page 41). 
Rochester, New York, a city of about 280,000 population is 
located 80 miles from Buffalo, a city of approximately 400,000 
people. The first State Route completed between these cities 
is shown on Fig. 13 as far as Batavia, a city of 14,000 people, and 
is designated on this map as Route A. This route was laid out 
in conjunction with State Route 6, the main east and west route, 
on the principle of local service and it has served very satisfac- 



GENERAL ENGINEERING LOCATION 



57 



torily for through traffic also. From the standpoint of through 
traffic between Rochester and Buffalo the route marked B on 
the map (Fig. 13) is the logical route and this will undoubtedly 
be built in the near future. That is, our experience indicates 
that it is better to first care for the local service and then in the 
future as the traffic requires it build new routes or partially re- 
locate old routes for the further advantage of long distance travel. 
A comparison of these two routes between Rochester and Batavia 
follows and shows the distinct advantage of Route B from the 
standpoint of through travel and Route A for local service. 



Length, miles 

Total rise and fall, feet 

Number of railway shipping points served . 

Total railroad crossings 

Railway grade crossings 

Overhead or subway railway crossings . . , . 



Route A 


Route B 


37 


31 


1850 


1400 


15 


9 


13 


4 


9 


1 


4 


3 



To give an idea of the traffic on this route in 1919 the following 

census (average 10 hour count in summer season) is shown at 

different points: 

Route A 





Horse traffic 


Motors 






1 horse 


2 horse 


Cars 


Trucks 


Total 


Between Rochester and Scotts- 
ville 


30 

70 
85 
15 


30 

40 

65 

10 
i 


850 

700 
1600 
1200 


100 

no 

180 ' 

85 


1010 


Between Scottsville and Cale- 
donia 


920 


Between Caledonia and Le Roy.. 
Between Le Roy and Batavia. . . . 


1930 
1310 



As an additional point of interest the new proposed through 
Route B from Bergen to Batavia fails to pass through two small 
settlements Byron and South Byron because it would be neces- 
sary to use 2 miles extra distance for this local service. That 
is, Route B primarily considers through service. These villages 
can be served by a stub line. It is often desirable to by-pass 
villages and even certain cities on through routes on account of 
traffic congestion and the annoyance and danger of a large volume 



58 LOCATION, GRADING AXD DRAINAGE OF HIGHWAYS 

of high speed trafl&c in the communities in question. These 
places can be served by stub hnes or supplementary loops. As 
a rule, ^-illages desire to have the main road pass directly through 
them on account of state aid in connection with their street 
paving and the additional business derived from traffic but the 
last featiu-e does not amount to much unless they happen to be so 




m oi^m^^^iJ{\fisi)M&:M^ 



Fig. 16.— Bardine Redstone project (State of Colorado). Note how this road 

shortens the communication from Paonia to Carbondale. 

located on the Kne that the traffic would naturally stop for some 
reason. 

Pioneer Location.— To give an idea of the factors entering 
into the selection of route in mountain districts, an example will 
be cited in Colorado (see Fig. 16). The project referred to is 
the Bardine-Redstone road through the Sopris national forest. 



GENERAL ENGINEERING LOCATION 59 

This road was selected for improvement and advanced in order 
of construction by the U. S. Forest Service for the following 
reasons . An examination of the map will show that by a short road 
about 30 miles long over McClure's pass the Carbondale and 
Paonia valleys can be directly connected. Without this road, 
it took a day's travel by rail to get from Carbondale to Somerset. 
The second reason for the road was to open up a promising farm- 
ing section along the upper Blackwater which had heretofore 
been confined to a cattle and sheep range on account of the 
impossibihty of getting produce to the railroads. By the con- 




FiG. 17. — Example of engineering grade reduction. Pack trail in foreground. 
Newly located wagon road to the right and above. U. S. forest road project. 

struction of moderately low cost natural soil road on a 5 or 6 per 
cent, grade over the low pass 3000 ft. above the valleys, inter- 
communication and new territory could be developed and a day's 
time in travel saved between two flourishing sections. 

The foregoing discussion indicates in a general way some of 
the factors governing route selection. 

Engineering Location. — A good detail location along the re- 
quired general route results in the most effective road for the 
traffic that can be obtained for the available funds. We control 
QUI desires for perfection by the limitations of the community 
pocketbook. It is obviously desirable to obtain short distance, 
easy alignment, reasonable grades and to avoid locations which 



60 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

call for extremely expensive construction such as rock work, 
flood areas, etc. It is ob\dously desirable to avoid locations where 
snow drifts badly or fails to melt promptly in the spring as the 
nmnber of days in a year that a road is open has a large effect on 
its usefulness. A summary of the engineering principles of 
location are given on page 148. 

Extreme Refinements Impracticable. — An economic engineering 
location for commercial roads might be theoretically developed 
on the lowest ton mile hauhng cost to traffic. Practically it 
is not yet reasonable to do this in many cases for the ordinary 
highway and the reasons for disregarchng this factor as the decid- 
ing element seem sound. Railroads have spent large sums to 
reduce the ton mile cost and in their location the engineers make 
extremely careful comparative estimates of construction cost 
against operating cost. They consider the elements of shorter dis- 
tance, curvature, light and heavy grades, etc. ^lany railroad 
engineers wonder why these considerations are not given more 
weight on highway work considering the increase in mechanical 
transport. One of the evident reasons is that railroads get a di- 
rect tangible money return in diWdends for their expenditure and 
the return to the community on a pubhc road investment is too 
intangible. However, as a matter of interest we include a 
discussion of the approximate relation of distance, rise and time 
as it affects operating costs on pages 79 to 114. This data has 
been used by the author for some time as a basis for judgment in 
the comparison of fines. 

It is undoubtedly true that to get the full value of an improved 
road system the engineering location must be made for the most 
efficient use of motor transport but at the present time there is 
no possibifity of obtaining or any justification for spending 
extremely large sums to reduce the haufing cost below that 
obtained by the usual modern highway design. If we had un- 
fimited funds pro^fided by truck owners a careful analysis would 
be justified on special commercial roads but we must consider 
the followincr facts: the location of roads in well settled districts 
are practicaUy confined to existing rights of way except for 
minor relocations to avoid extreme grades or for safety reasons; 
this is necessary as the community has grown up along these well 
set routes and the principle of direct contact holds. These rights 
of way were not necessarily laid out with any regard to economic 
road location and in fact are often arbitrarily fixed by land 



GENERAL ENGINEERING LOCATION 61 

section lines or locations where a poor road could be constructed 
in the past without much labor or cost. The cost of new rights 
of way for entire new locations and the difficulties of acquiring 
are prohibitive at this stage of development in road building 
except for unusual cases. The improved roads of today are only 
a progressive stage in the development of highway transport. 
The demand for them and the satisfaction in their use lies 
mainly in the fact that they provide a firm surface which can 
be used the year round, that they materially cheapen the cost 
of hauhng that they make the use of light automobiles feasible 
for long and fast trips. The community is willing to pay a certain 
amount for the improvement in road conditions which the usual 
practice in modern road construction gives but it is not willing 
to pay large additional sums for further reduction in ton mile 
hauhng costs. In the first place only a comparatively few men 
would get a direct benefit from such expenditure. The indirect 
return to the community is too intangible. Much of the road 
traffic is pleasure traffic and a few more gallons of gas means 
nothing. If the owner did not spend his surplus for gas, he 
would spend it for ice cream soda or the movies. There seems 
to be no way of making the few road users who would benefit 
by a further reduction in hauling cost pay the price of the neces- 
sary construction. It may be that for certain toll roads some 
time in the future or for exceptional present cases in metro- 
politan districts we can use a ton mile cost location analysis but 
we are not yet up to this standard for the usual road. 

This does not mean that the engineer should not make an 
effort to get the best possible location that he can but he should 
bear in mind that the first principle of general policy considering 
a comprehensive road system is Mileage Service and aim to get the 
greatest mileage of road that will serve the purposes of the great 
majority of road users. For all roads except special service 
commercial roads probably 90 per cent, of the traffic does not 
demand nor would it be particularly benefited by excessive 
refinements. Poor grades or alignment should never be used 
on high class roads as they are the fundamental features of the 
improvement and the only permanent features of construction. 
Liberal expenditures are justified but there is a limit to expend- 
itures for refinements that reduce mechanical operating costs to 
a minimum. The detail analysis of grade alignment section, 
etc. given in Chapters 4 & 5 are intended to bring out the re- 



62 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

quirements of road design that are necessary for the satisfaction, 
safety, comfort and comparative cheap hauhng requirements of 
the average road users. These are the fundamentals which must 
be provided. 

We will attempt to show the road value of different Hmiting 
engineering requirements with their effect on construction cost. 
Additional refinements beyond the fundamental requirements are 
desirable if the funds are available from the proper sources. 
By the proper sources are meant the actual road users benefited 
by the additional cost of construction. 



^V^'*... sr^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^H 


■I^^^H 








' , '\" 



Fig. is. — A Utah road location. 



Saving in distance is valuable, saving in total rise is valuable, 
easy grades and the eh'mination of sharp curves are desirable. 
Every effort is made to accompHsh these results utihzing the 
existing roads where we have to, making minor relocations to 
avoid extreme grade or danger because the sentiment of the 
community approves these measures but always bearing in 
mind that today and for a long time to come mileage is the prime 
requisite of programs. It is possible and desirable in the 
sparsely settled communities to make better engineering locations 
and for such districts we can more nearly accompHsh a reasonable 
analysis as far as right of way handicap is concerned but in these 
districts shortage of funds often plays havoc with our intentions. 



GENERAL ENGINEERING LOCATION 63 

Value of Saving Distance and Rise. — It is well to bear in 
mind what distance saving is worth and what a saving in total 
rise is worth. The data given is, of course, of only general value 
as the fluctuating cost of motor operation, the types of hauHng, 
special conditions of all sorts affect the figures. They, however, 
show in a general way that it is well worth w^hile to reduce traffic 
losses arising from these elements of needlessly poor location or 
design. 

Mr. A. R. Hirst gives the following conservative figures on 
the value of saving distance: 

''If the very conservative sum of 10c. per mile is allowed for each mile 
of travel saved, the saving of a mile in distance on highways carrying 
the following average number of vehicles per day will save the traveling 
public the given amount per year, which is the interest at 5 per cent, on 
the amount given in the third column. 

Value of a Mile in Highway Distance Saved 



Average number of 


Saving to owners 


Saving capitalized 


vehicles per day 


per year 


at 5 per cent, equals 


100 


$ 3,650 


$ 73,000 


250 


9,125 


182,500 


500 


18,250 


365,000 


750 


27,375 


547,500 


1,000 


36,500 


730,000 


2,000 


73,000 


1,460,000 


5,000 


182,500 


3,650,000 


10,000 


365,000 


7,300,000 



The value of ehminating rise cannot be figured with any 
degree of accuracy as there are too many indeterminate and vari- 
able factors but in the author's opinion it is not likely that the 
capitalized value of saving in yearly operation due to elimination 
one foot of rise and fall per 100 vehicles per day on long routes 
will exceed $30 on light grades or $400 on heavy grades. For 
small grading reductions on short hills the time factor is of no 
consequence and the practical value of saving a foot rise and fall 
is not probably more than one-third of these figures (see pages 
79 to 114). 

It is very evident that considerable expenditure is justified 
to reduce distance and rise but it is also evident that it would be 
impracticable to carry this method of location to its logical 
conclusion by expenditures in any way approximating the figures 
given. That is, the location of a free public road financed by a 



64 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

general tax with no direct revenue return can hardly be analyzed 
from the same point of view as a trunk Une railroad. 

Relocations of Existing Highways. — We all would prefer to 
have scientifically located highways. A great many engineers 
believe that the time has come to make extensive relocations. 
It is self evident that relocations which reduce the construction 
cost of the proposed road as well as reduce motor operation 
costs should be made at once. It is surprising how often even 




Fig. 19. — Relocation Galena-summit highway. U. S. forest road project 
(State of Idaho). Old road, 15 to 20 per cent, grades. New location (dotted 
line), 6 per cent, compensated on sharp curves. 

Note. — Relocations of this kind are most certainly justified at the present 
stage of our highway programs. 



such relocations are not made and it is desirable to impress on 
the men in charge of surveys that they should continually bear 
in mind the necessity of such relocations and not feel that they 
must follow the present road lines where these conditions prevail. 
There seems to be no question that expenditures for relocations 
necessary to obtain reasonably good grades and alignment 
are justified at the present stage of our road programs but the 
author beUeves that extensive relocations involving excessive 



GENERAL ENGINEERING LOCATION 



65 



refinements must be gradually worked out except for a few ex- 
treme cases and that practically it will be easier to accomplish 
and fairer to the general public to do most of this work under 
Reconstruction Programs financed by direct vehicle taxes rather 
than to attempt it at this time.^ 

In case a relocation is necessary no halfway measures should be 
allowed. In too many cases even on fairly important state roads 
in rich communities relocations have been made on the basis of 
9 per cent, grades when it was perfectly possible to get 7 per 
cent, or less. Halfway treatments of this kind are worse than 
nothing. 




Fig. 19A. — Airplane view of bridge approach relocation (New York state). 
Minimum radius curvature old road 60'. Minimum radius curvature new 
road 570'. This relocation adds materially to the safety and convenience of 
travel. 

To illustrate present practice on relocations the following 
quotations from the Iowa Highway Dept. Field Manual is given. 
The limiting grade of 6 per cent, mentioned does not agree with 
the author's recommendation given on page 116, but the general 
scope of the data strengthens the discussion at this point. 

1 See pages 104-107 for an approximate basis of comparing the value of 
alternate location. 
5 



66 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Relocation.'^ — ''Where the topography is flat or gently roUing the 
profiles readily lend themselves to satisfactory grades at a moderate 
cost, and relocations to any extent are seldom necessary. But in the 
rougher country relocations will frequently be necessary and the field 
man must constantly watch for opportunities to better the ahgnment, 
avoid steep hills, or improve stream crossings by relocations. The 
necessity for or advisability of relocating must always be balanced 
against the cost, and in general it is true that a proposed change of 
any magnitude is advisable only when it can be shown that such 
change will be economical or will produce a decidedly better road. It 
is therefore important that the cost of relocation be thoroughly investi- 
gated. In this connection the field man must remember to take into 
consideration the various improvements along the exsiting road, such 
as farm buildings, orchards, permanent bridges and culverts, heavy 
cuts and fiUs, etc. 

The following instructions should be followed: 

(a) In all cases where it appears that an excessive amount of earth- 
work will be required to reduce the present road to 6 per cent, grades, 
the possibihty of relocations to reduce grades to 6 per cent, or less 
shall be fully investigated. 

(b) In cases where there is a succession of grades which may be re- 
duced to 5 or 6 per cent., but which cannot be reduced below that 
figure without considerable work, the question of relocation should be 
fully investigated. 

(c) In case of doubt as to the feasibiHty of any relocation, a survey 
should always be made. 

(d) In all cases where relocations are surveyed a survey shall be 
made on the old road also. 

(e) In the case of minor relocations the margins of the old roadway 
should always be shown by a sketch indicating the old roadway by 
dotted lines, and by data in the cross section notes. In such cases the 
survey of the old road may consist only of extending the cross sections 
over the same. 

(/) The notes shall show which location is to be used or shall state 
that the determination of which route to follow cannot be made until 
the notes are worked up in the office. The chief of party shall enter 
this notation in the field notes after consultation with the district 
engineer." 

Conclusion. — Large bond issues have the habit of disappearing 
without accompUshing as much as they were expected to accom- 
plish and any unusual feature of design, either location or pave- 
ment, which raises the average cost per mile must be used with 
caution. The great need of most localities is a fairly complete 

1 Iowa Highway Dept. Manual. 



GENERAL ENGINEERING LOCATION 67 

road system usable the year round. Until this is accomplished 
extreme refinements have a doubtful value. 

Before large expenditures are made for unusual refinements in 
location it is just as well to get a reasonably complete mileage of 
good usable firm surfaced roads, as 100 miles of the usual modern 
improved road with reasonably good grades and alignment are 
more valuable to the community as a whole than 50 miles of 
more scientifically located highways. Needlessly short mileage 
is the most serious criticism that can he made of any general policy 
dealing with an incomplete road system. 

It is not probable that the foregoing general discussion is of 
much interest to most of the younger engineers. It has been 
included more in the nature of a general survey of the problem. 
Nine-tenths of the road men are more interested in how to make a 
detail design of a definite road. The detail theory of design will 
be taken up in the following order: Grades, alignment, sections, 
drainage (pavements, Vol. 2.) 



CHAPTER IV 
GRADES AND ALIGNMENT 

GRADES 

Grade line design considers the proper use of maximum, mini- 
mum, intermediate and adverse grades and their vertical curve 
connections. Grade line design in connection with align- 
ment considers the relative values of distance against rise 
and fall. 

The effect of grade may be roughly summarized as follows: 

An increase in the rate of grade decreases the load that can be 
hauled up the grade for a fixed power. 

An increase in the rate of grade increases the expenditure of 
energy to maintain a fixed speed climbing the grade. 

An increase in the rate of grade decreases the speed for a fixed 
power. 

An increase in the rate of grade increases the wear and tear on 
mechanical outfits. 

The mechanical energy expended in climbing is partially 
balanced by the reduction of energy expended on down grades. 

The mechanical energy expended in climbing affords a very 
definite basis of comparison of the value of travel in one direction. 
The expenditure of energy on dowi/ grades is indefinite and while 
it effects the total operating cost on a grade it cannot be given as 
much weight in the conclusion as the first method. The effect 
of grade on the depreciation and repair of mechanical equipment 
is indefinite but it is certain that it bears some relation to the rate 
of grade. 

Grade selection depends on considerations of safety, con- 
venience, traffic operating cost, and the cost of construction and 
maintenance. Cost of traffic operation is not always the most 
important factor. It must often give way to considerations of 
safety or initial construction cost. 

Reasonably low rates are desirable. The whole question of 
grades lies in the decision of what is reasonable for a specific case. 

68 



GRADES AND ALIGNMENT 



69 



A summary of practical rules for location and cut and fill grade 
line design is given at the end of the chapter. 

Maximum Grades. — Suppose we consider the subject of maxi- 
mum grades from the following standpoints: 

1. Relative importance of horse and automobile traffic in the 
selection of grade. 

2. Effect of grade on horse traffic. 

3. Effect of grade on motor traffic. 

4. Current practice in maximum grades. 

5. Practical considerations governing the selection of grade. 

6. Effect of ruling grade on cost. 

7. Recommended general practice. 

Relative Importance of Horse and Auto Traffic in the Selection 
of Maximum Grade. — Tables 2 and 2A show the rapid growth of 
motor traffic on the main roads of Massachusetts and the general 
character of the traffic on secondary roads in Western New York. 



Table 2 





1912 


1915 


1918 


Per cent. 

of increase 

G years 


Automobiles and trucks. . . 

Motor cycles 

Operators and chauffeurs. 
Motor vehicle fees 


50,132 

5,034 

65,600 

$616,236 


102,633 

9,520 

133,700 

$1,235,723 


191,019 

12,708 
225,272 

$2,159,257 


280 
150 
240 
250 


Average Daily Traffic on M 


A.IN Roads in Massachi 


JSETTS 




1909 


1912 


1915 


1918 


Per cent. 

of increase,' 

9 years 


Light horse 


91 

88 


68 

88 


40 

72 


24 
43 


- 73K 

- 51 


Heavy horse. . .• 






Total horse 


179 
131 


156 

280 

17 


112 

555 

45 


67 

923 

75 


- 623^ 
+604 
+3411 


Automobiles and light trucks . 
Heavy trucks 


Total motors 


131 


297 


600 


998 


+661 






Total vehicles 


310 


453 


712 


1,065 


+243 











1 In 6 years. 



70 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 
Per Cent, of Total Traffic 





1909 


1912 


1915 


1918 


Light horse 


29 

28 


15 
19 


5K 
10 


2 


Heavy horse 


4 






Total horse 


57 
43 


34 

4 

62 


153^ 

78 


6 


Trucks 

Motors 


7 
87 



Table 2A. — Daily Traffic Counts on Selected "Local Service- 
State County Roads in Western New York 



Number 


Number 

of 

miles 


Horse traffic 


Motor traffic 


of 
roads 


1 horse 


2 horse 


Total 
horse 


Light 
cars 


Trucks 


Total 
motors 


14 


60 


45 


39 


84 


250 ' 


36 


286 



Horse traffic per cent, of total. 
Motor traffic per cent, of total. 



23 

77 



Note. — On the main State Route Roads the percentage of horse traffic 
corresponds very closely with the Massachusetts results given in Table 
No. 2. 



We are all familiar with this change in the character of highway 
traffic. Maximum grades have a radically different effect 
on horse and single unit motor traffic and it is necessary to come 
to some reasonable conclusion as to which kind of travel should 
govern the design. There is a strong tendency to consider grade 
fine design from the standpoint of single unit motor hauKng on 
account of the predominance of this traffic on improved roads. 
As far as distance and total rise and fall are concerned this is 
probably sound. As far as rate of grade is concerned the author 
has no hesitation in saying that he considers it better to give 
horse traffic the preference on all town and county roads and that 
the conclusions as to grade that will be satisfactory for horse 
traffic will probably satisfy motor traffic on most state and 
national routes also. This conclusion is based on a number of 
factors. As long as horses are used for general farm utility they 
will be used for some hauling even under conditions favorable for 



GRADES AND ALIGNMENT 71 

trucks (see Table 2A). In the northern states snow and ice 
handicap motor transport for a portion of the year particularly 
on side feeder roads. It is not hkely that horse traffic will be 
entirely ehminated from our improved roads. Maximum 
grades hmit the load a team can haul but they do not handicap 
single unit truck operation on firm surfaced roads as all the fight 
and heavy motors have sufficient excess power to haul their 
rated load up any grade within reason. Steep grades do fimit the 
appfication of the long trailer train mode of haufing. Where this 
method is popular or where special conditions make its adoption 
fikely maximum grades may well be reduced below even the rates 
considered satisfactory for horse traffic. The long trailer train, 
however, is not a general utifity system and need not as a rule 
determine the rufing grades except for a few special service 
roads. Long steep grades do affect the ease of motor traffic by 
forcing the driver to drop into second or low gear but they do 
not reduce single unit truck capacity nor do they have much 
effect on fuel consumption provided the total rise and fall and 
distance between terminals is the same. 

It therefore seems safer to design maximum grades for a 
reasonable load for the weaker mode of haufing and in this way 
satisfy all classes of traffic. The final selection of grade is also 
affected by considerations of safety, convenience and the cost of 
construction and maintenance. 

MAXIMUM GRADES FROM THE STANDPOINT OF HORSE TRAFFIC 

Difficulty of Ascent and Safety of Descent. — The factors 
controlfing ease and safety of ascent and descent have different 
values for different surfaces, but as most of the roads will in 
time be hard surfaced and as all parts of the design should fit 
into the final improvement, this part of the grade argument is 
made primarily for hard surfaced conditions. 

European observers claim that on a stone road 5 per cent, is 
the maximum grade that can be descended safely by a trotting 
team without brakes and that 12 per cent, is the maximum that 
can be safely descended with brakes. By the use of the sfiding 
shoe or locked wheels freighters in the Rockies descend 20 per 
cent, grades without much difficulty on ordinary natural soil 
roads. Safe descent with brakes need not be considered except 
in rare cases' as it would result in a grade far beyond ordinary 



72 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

practice. Safe and easy descent without brakes is more impor- 
tant for Kght rigs than for heavy hauhng but as this class of 
traffic has been practically eliminated by cheap automobiles it 
need not be given much weight. Descent, therefore, plays only 
a minor part in grade selection except where the alignment is bad. 

Hauling Power. — The writer knows of no careful records of 
actual maximum loads that can be hauled up different hard 
surfaced grades by an ordinary team; it is probably better to 
discuss this point theoretically as any experiments would be 
affected by too many variable local conditions to be worth much 
as a basis of comparison. As a check on the theoretical discus- 
sion records of loads on extreme mountain grades are given 
on page 78 which show that for all practical purposes. Table 
8 of theoretical loads is fairly close and is on the safe side. 

A summary of Prof. I. O. Baker's discussion of maximum 
team loads is given below, and through his courtesy we are 
enabled to include a collection of tables taken from his work, 
''Roads and Pavements." 

Various trials have determined that the normal tractive power 
of a horse travehng three miles per hour for ten hours a day is 
approximately one-tenth of its weight; that when hauhng up a 
steep grade it can exert one-fourth of its weight for a short time; 
that for a continuous exertion of one-fourth, the grade should not 
be over 1200 ft. long and if over that, resting places should be 
provided every 600 to 800 ft. ; that in starting and for a distance 
of 50 to 100 ft., one-half of its weight can be used; and that the 
net tractive power ordinarily exerted by a horse on a grade equals 
(^'i its weight) — (the effort required to hft itseh) or approxi- 
mately (0.25 W) — {W X per cent, of grade expressed in 
hundredths), i.e., (0.25 W — 0.04 W) for a 4 per cent, grade. 
This undoubtedly gives a reasonable basis for ordinary hauhng 
conditions but from data obtained by the author in connection 
with freight hauhng in mountain regions it is evident that a good 
draft horse ^dll exert more than 0.25 W on moderately short 
sharp pitches of a long chmb if allowed to rest at intervals of 
200 to 300 ft. The evidence indicates that a value of 0.35 W is 
about right for such conditions. 

Table 3 shows the effective power developed by an ordinary 
team of 1200-lb. horses with moderate exertion and Table 3 A 
the power of a first class team of 1600-lb. horses exerting their 
full strength. 



GRADES AND ALIGNMENT 
Table 3. — Ordinary Stock Moderate Exertion 



73 





Grade, 
per cent. 


Theoretical net 
tractive effort 


Tractive 
effort in lbs. 




Level 


0.10 TT 


240 




23^ 


0.25 W - PW 


540 


W = weight of team 2400 lbs. 


4 


0.25 W -PW 


504 




5 


0.25 W -PW 


480 


P = per cent, of grade in hun- 


6 


0.25 W -PW 


456 


dredths. 


7 


0.25 W -PW 


432 




8 


0.25 W -PW 


408 




9 


0.25 W -PW 


384 




10 


0.25 W -PW 


360 



Table 3A. — Draft Stock 


Full Power 






Grade, 


Theoretical net 


Tractive 




per cent. 


tractive effort 


effort in lbs. 




5 


0.35 W -PW 


960 




6 


0.35 W - PW 


928 




7 


0.35 W -PW 


896 


W = weight of team 3200 lbs. 


8 


0.35 W -PW 


864 




10 


0.35 W - PW 


800 


P = per cent, of grade in hun- 


12 


0.35 W -PW 


736 


dredths. 


14 


0.35 W -PW 


672 




16 


0.35 W - PW 


608 




18 


0.35 W -PW 


544 




20 


0.35 W -PW 


480 




22 


0.35 W -PW 


416 



Grade and Rolling Resistance. — This power is used in over- 
coming axle friction, gravity resistance and rolHng resistance. 

The axle friction is small amounting to three or four pounds 
per ton for American farm wagons. 

Grade resistance (gravity) equals (load X per cent, of grade 
expressed in hundredths) and expressed in pounds per ton of 
load equals (2000 X P). 

The rolling resistance varies for different surfaces and for 
each surface depends on the diameter of wheel, width of tire, 
speed of travel and the presence or absence of springs on the 
wagon. The best diameter of wheels, best width of tires and the 
use of springs as they affect the ease of hauling for both farm and 
road use are problems for the wagon manufacturers. 



74 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Morin, a French engineer, concluded from a series of careful 
experiments that the harder the surface of the road the less 
effect width of tire had on rolhng resistance. We are arguing 
from the standpoint of comparatively hard surfacing and are 
dealing with small differences in wheel diameter and can dis- 
regard these factors. As a matter of interest Tables 4 to 6 are 

Table 4. — Effect of Width of Tire upon Tractive Powers 
Resistances in Pounds per Ton 



Ref. 
No. 



Description of the 
road surface 



Diameters of the front and rear wheels respectively 


3 '-6" & 
3'-l0" 


3'-6" & 
3'-10" 


3'-8" & 
4'-6" 


3'-6" & 
3'-10" 


3'-8" & 
4'-6" 


Width of tires 



IH" 4" IH 4" IH" 4" IM" 3" IH" 3" 



Sod 

Earth road (hard) . . . 
Earth road (muddy) . 
Sand road (hard) . . . . 
Sand road (deep) . . . . 
Gravel road (good) . . 
Wood block (round) 



199 
371 

51 



108 
243 
162 
351 

49 



268 
171 

98 
61 



304 
164 

117 
70 



236 
141 

83 
35 



254 
168 

80 
46 



283 
152 



239 
152 



54 



189 
114 
265 



66 

28 



228 
114 
228 



76 
38 



1 Pamphlet by Studebaker Brothers Manufacturing Company, 1892. 



Table 5. — Effect 'of Size of Wheels on Tractive Resistance^ 

Pounds per Ton 



Ref. 
No. 



Description of road surface 



Mean diameter of 

front and rear 

wheels 



50" 38" 26" 



1 

2 
3 

4 
5 
6 
7 
8 
9 
10 



Macadam, slightly worn, fair condition 

Gravel road, sand 1 in. deep, loose stones 

Gravel road, upgrade 2.2 per cent., ^ in. wet sand, 

frozen below 

Earth road. Dry and hard 

Earth road. 3^ in. sticky mud, frozen below 

Timothy and blue grass sod, dry grass cut 

Timothy and blue grass sod, wet and spongy 

Cornfield; flat culture across rows, dry 

Plowed ground; not harrowed, dry and cloddy 

Average value of tractive power 



57 

84 

123 
69 
101 
132 
173 
178 
252 



61 
90 

132 
75 
119 
145 
203 
201 
303 



130 



148 



70 
110 

173 

79 
139 
179 
281 
265 
374 



186 



1 Experiments of Mr. T. I. Mairs at the Missouri Agricultural Experi- 
ment Station. 



GRADES AND ALIGNMENT 



75 



included to show the results of experiments on different soils 
and roads. 

The question of wide tires affects road design chiefly in con- 
nection with the distribution of load over a safe area and will 
be taken up under ^^Foundations" (second book of this series). 

Table 6. — Tractive Resistance of Broad and Narrow Tires^ 
Resistance in Pounds per Ton 



Ref. 
No. 



Description of road surface 



Width of tire 



m 



6" 



No. of 
trials 



9 
10 

11 
12 
13 
14 
15 
16 
17 
18 
19 
20 

21 

22 
23 

24 



Broken stone road; hard, smooth, no dust, no loose stone. 

Gravel road; hard and smooth; a few loose stones 

Gravel road; hard, no ruts, large quantity of sand 

Gravel road; new gravel, not compact, dry 

Gravel road; Wet, loose sand 1 to 2J-2 in. deep 

Earth roads. Loam, dry, loose dust 2 to 3 in. deep 

Earth roads. Loam, dry and hard, no dust, no ruts, nearly 

level 

Earth roads. Loam, stiff mud, drying on top, spongy 

below 

Earth roads. Loam, mud 23'^ in. deep, firm below 

Earth roads. Clay, sloppy mud, 3 to 4 in. deep, hard 

below 

Earth roads. Clay, dry on top but spongy below 

Earth roads. Clay, dry on top but spongy below 

Earth roads. Clay, Stiff deep mud 

Mowing land. Timothy sod, dry, firm, and smooth . . 

Mowing land. Timothy sod, moist 

Mowing land. Timothy sod, soft and spongy 

Pasture land. Blue grass sod, dry, firm, and smooth .... 

Pasture land. Blue grass sod, soft 

Pasture land. Blue grass sod, soft 

Stubble land. Corn stubble, no weeds, dry enough to 

plow 

Stubble land. Corn stubble, some weeds, dry enough to 

plow 

Stubble land. Corn stubble, in Autumn, dry and firm. . . 
Plowed land. Freshly plowed, not harrowed, surface 

rough 

Plowed land. Freshly plowed, harrowed, smooth, com- 
pact 



121 


98 


182 


134 


239 


157 


330 


260 


246 


254 


90 


106 


149 


109 


497 


307 


251 


325 


286 


406 


472 


422 


618 


464 


825 


551 


317 


229 


421 


305 


569 


327 


218 


156 


420 


273 


578 


436 


631 


418 


423 


362 


404 


256 


510 


283 


466 


323 



1 Missouri Agricultural Experiment Station Bulletin No. 39. 

Table 7 gives the average rolling resistance in pounds per 
ton of load on different pavements for the ordinary farm wagon 
driven at ordinary speeds. 

Effect of Grade on Loads. — For a comparative estimate we 
will take a value of 40 lbs. per ton of load, including axle friction, 
on macadams and rigid pavements and 100 lbs. per ton for 
earth roads in fair shape. The resistance to the effective tractive 



76 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Table 7^ 



Kind of pavement 



Asphalt 

Brick or concrete 
Cobble stones. . . . 

Earth roads 

Gravel roads 

Macadam roads. 

Plank 

Stone block 

Wood block 



Rolling resistance 

in lbs. per ton 

of load 



30 to 70 
15 to 40 
50 to 100 
50 to 200 
50 to 100 
20 to 100 
30 to 50 
30 to 80 
30 to 50 



^Baker's 'Roads and Pavements." 

power of the team per ton of load is therefore 40 + (2000 X P) 

on hard surfaced roads, and 100 + (2000 X P) for earth roads, 

and the maximum load expressed in tons for any grade equals 

/ Effective tractive power of team for that grade \ 

\ Resistance per ton of load for that grade / 

Using the tractive powers of the ordinary team shown in 

Table 3, the following table is constructed. It is chiefly useful 

for a comparison of the effect of grade on load but all evidence 

indicates that the loads given correspond closely to practice. 

Table 8A shows loads for extreme team exertion as compiled 

in Table 3A. The loads given include weight of wagon. 

T.\BLE 8 





Effective 

tractive 

effort, 

lbs. 


Improved roads 


Earth roads 


Grade, 
per cent. 


Resistance in 
lb. per ton 
of load 


Maximum 

load in 

tons 


Resistance, Max. load, 
lb. tons 


Level 


240 


1 

40 6.0 


100 2.4 


23^ 


540 


90 ; 6.0 


150 3.6 ■ 


4 


504 


120 


4.2 


180 2.8 


5 


480 


140 


3.4 


200 1 2.4 


6 


456 


160 


2.9 


220 


2.1 


7 


432 


180 


2.4 


240 


1.8 


8 


408 


200 


2.0 


260 


1.6 


9 


384 


220 


1.7 


280 


1.4 


10 


360 


240 


1.5 


300 ! 1.2 



GRADES AND ALIGNMENT 
Table 8A. — Draft Stock Extreme Exertion 



77 



Grade, 
per cent. 



Effective 

tractive 

effort 

lbs. 



Hard surfaced roads 



Earth roads 



Resistance 
in lb. per ton 



Maximum 
load in tons 



Resistance 
in lb. per ton 



Max. load 
in tons 



5 

6 
7 
8 
10 
12 
14 
16 
18 
20 
22 



960 
928 
896 
864 
800 
736 
672 
608 
544 
480 
416 



140 
160 
180 
200 
240 
280 



6.8 
5.8 
5.0 
4.3 
3.3 
3.0 



200 
220 
240 
260 
300 
340 
380 
420 
460 
500 
540 



4.8 
4.2 
3.7 
3.3 
2.7 
2.2 
1.6 
1.4 
1.2 
1.0 
0.8 



Effect of Length of Grade on Maximum Load. — In mountain 
road design where a long ruling grade is used it is often economical 
to introduce short stretches of steeper grade to avoid extremely 
expensive construction and to improve aHgnment. In order to 
determine the maximum short grade (not exceeding 300 ft. in 
length) that can be used in connection with a long ruHng grade 
without reducing the team load we have compiled Table 8B 
for a 2400-lb. team. 

Table 8B. — Equivalent Long and Short Grades for Hard Surfaced 

Conditions 



Long Ruling Grades Tractive effort 0.25 
W 2400 lb. team 


Short Maximum Grades Tractive effort 0.35 
W 2400 lb. team 


Grade, per cent. Maximum load, tons Grade, per cent. 


Maximum load, tons 


5 
6 

7 
8 


3.4 
2.9 
2.4 
2.0 


7 

9 

101 
12 


3.7 
2.8 
2.5 
2.0 



1 12 per cent, is the practical limit (on account of safe descent) on any road 
of sufficient importance to be considered from an engineering standpoint. 

This principle can also be applied to a long cut and fill grade 
reduction with a very material saving in cost but if used the 
steeper rate should not be over 250 to 300 ft. long and should be at 
the bottom of the hill. 



78 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



RECORDS OF TEAM LOADS 

We are indebted to Mr. H. G. McPheters and F. F. Roberts 
for the following data on team freighting in the Rocky Mountain 
region. It is practical data obtained from personal experience 
and strengthens the force of the theoretical discussion. The 
loads given are net and do not include wagon weights. They 
represent usual freighting loads which are practical maxima. 

Heber Fruitland Road, State of Utah 

Daniels Canyon Section 

Earth road in fair shape. 

Long 8 per cent, grades. 

Short 15 per cent, grades. 

Net load for four horse team 3500 lb. (during summer). 

Galena Summit Road, State of Idaho 

(See Illustration, page 64) 

Natural soil road in fair shape 
Maximum grade (Salmon River side) 20 per cent. 
Maximum grade (Wood River side) 17 per cent. 
Load for one team 1800 lb. (during summer). 
Load for two teams 4000 lb. (during summer). 

Load for three teams (six horses and two wagons loaded 5000 lb. on lead 
wagon and 4000 lb. on trail taking one wagon at a trip up the mountain.) 

Trail Creek Summit Road, State of Idaho 

Natural soil road (fair condition during summ.er). 

Maximum grade 22 per cent. 

Load for one team 1200 lb. 

Load for two teams 2500 lb. 

When freighting by teams was the principal mode of transportation, 
there were used on this road several outfits of twenty-four mules hooked 
to four wagons loaded about as follows: Lead 14,000 lb.,' lead swing 10,000 
lb.; swing 8,000 lb. and trail 4000 lb. Two men handled the whole outfit 
which was certainly a man's job. 

Rocky Bar Atlanta Road Over Bald Mountain 

Natural soil. 

Maximum grade 16 per cent. 
Load for one team 2000 lb. 
Load for two teams 4000 lb. 

A large amount of freight is carried over this road by auto trucks at the 
present time. 



GRADES AND ALIGNMENT 79 

The Theoretical Advantage of Certain Grades. — From Tables 
8, 8A and SB and the previous discussion we can pick out the 
grades that theoretically fulfill certain traffic requirements. 

I. On hard surfaced roads the same load that can be drawn up 
a 2}^ per cent, grade by reasonable extra exertion of a team, can 
be hauled on a level with ease. This makes a perfectly balanced 
design from the standpoint of team hauling. The theoretical 
load is six tons. For earth roads 5 per cent, fulfills this same 
condition with a theoretical team load of 2.4 tons. 

II. Five per cent, is the maximum grade that fulfills the re- 
quirement of safe descent at a trot without brakes. This is of 
httle importance under modern traffic conditions. 

III. The same load that can be hauled up a 7 per cent, hard 
surfaced grade can be drawn on a level dirt road in fair condition; 
a 7 per cent, grade therefore does not reduce the load of a team 
which must travel over even a level earth road for part of the 
distance. The theoretical load is 2.4 tons. 

IV. The use of short maximum grades of greater rate than 
the long ruling grades does not reduce the maximum load pro- 
vided they are proportioned as follows for hard pavements and do 
not exceed 250 ft. to 300 ft. in length. 

Long 5 per cent. Short 7 per cent. 

Long 6 per cent. Short 9 per cent. 

Long 7 per cent. Short 10 per cent. 

Long 8 per cent. Short 12 per cent. 

V. Twelve per cent, is the practical limit of grade for even 
unimportant roads on account of safe team descent with heavy 
loads. . 

As a matter of fact the selection of grade depends more on the 
requirements of the traffic and the topography of the country 
than on these theoretical advantages. 

Effect of Grade Selection on Motor Traffic. — It is not possible 
with the data at hand to analyze the cost of motor operation 
closely for different rates of grade but certain fundamental 
principles of road location can be established by the principles of 
mechanics modified by judgment. 

Reduction in distance, time of travel and needless rise and 
faU are desirable but it is very difficult to put a money value 
on such savings particularly the elements of time and rise. 

Practically, a little extra gas means nothing to a large pro- 



80 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS , 

portion of road traffic and a little extra time means even less, 
for we all waste a good share of our time despite the teachings of 
efficiency. Therefore to attempt to place a construction value 
on the saving of a Httle fuel and time hardly looks reasonable 
for most conditions. Under certain conditions, however, such as 
long distance main roads particularly where regular systematic 
truck freighting occurs the time element is a real factor and 
should be considered. The author has been in the habit of 
ehminating the time factor in considering motor traffic on Local 
Service roads but gives it some weight for Special Service Com- 
mercial roads. This, as a general rule, means that about twice 
as much expenditure is theoretically justified for saving dis- 
tance and about three times as much for saving rise on Special 
Service roads as on Local Service Roads. 

The discussion will first develop certain general principles of 
principles of location and then a rough approximation of operat- 
ing costs on different grades. The theoretical discussion is 
followed by data modified for practical use. (See table 125.) 
The author hesitated to include tables 11 to 125 in this book 
but finally decided to do so largely as a matter of academic 
interest as it is necessary for some one to make a start along 
these lines. The tables will undoubtedly be subjected to severe 
criticism. They can most certainly be improved by investiga- 
tion and experiment but they have been used for some time as a 
basis for judgment and their apphcation has resulted in what 
appears to be rational conclusions. They certainly demonstrate 
general principles of design and their use for detail conclusions is 
better than guesswork. They are submitted as a pioneer 
attempt which I hope wiU arouse discussion and further 
experimental investigation. 

EFFECT OF MAXIMUM GRADE ON MOTOR TRAFFIC 

Ascent and Descent. — ^Light and heavy single unit trucks 
(trucks without trailers) are commonly operated on firm surfaced 
roads up and down 15 per cent, grades. Light passenger cars 
have no difficulty in climbing 15 per cent, grades even on fairly 
poor natural soil roads. The safety of descent depends largely 
on the ahgnment, the condition of the road surface and the 
brakes but for a well equipped car on safe alignment it is not a 
noticeable factor in design up to 12 per cent, which is beyond 



GRADES AND ALIGNMENT 81 

the reasonable bounds of modern practice in grade selection. 
That is, the factors of climbing power and safe descent do not 
affect the selection of grade from the standpoint of single unit motor 
transport. Trailer train motor transport, however, demands 
low ruling grades. It should, however, be remembered that 
this type of hauling is comparatively slow. That it increases 
the danger to ordinary traffic and clutters up the road. That it 
can not be considered as a probably popular general utility 
method and that only in rare special cases would we be justified 
in large expenditures at this time for the purpose of reducing 
maximum • grades below that required for a truck with one 
trailer in order to increase the train capacity. 

Record of Truck Performance. — We are indebted to the Pierce 
Arrow Motor Car Company for the following chart which shows 
the abihty of their trucks to pull on different kinds of road 
surfaces and different grades. This data confirms the previous 
statement that modern trucks have sufficient power to easily 
handle their full loads on any grade that would be selected for 
horse traffic on improved roads. (Chart, page 82.) 

Convenience of Operation. — Drivers dislike to be forced 
into second or low gear. If it is possible to approximately 
determine the rate of grade at which most cars or trucks shift 
gear this has some bearing on grade selection. It is, of course, 
difficult to figure this closely as motor design improves, gear 
ratios vary; cars run on varying degrees of efficiency, gasoline 
varies in quafity, etc., but as a matter of interest the author's 
experience indicates that the average light pleasure car of the 
year 1919 shifts into second gear at about 7 per cent, and that 
very httle gear shifting is necessary on long 6 per cent, grades. 
W. C. Slay ton, a truck fleet manager, says that his 5-ton standard 
gear ratio trucks generally drop into second at about 5 per 
cent, and that very little shifting would be required on long 
4 per cent, grades. Passenger autos drop into low at about 
10 per cent, and the 5-ton trucks into low at about 8 per cent. 

From the standpoint of convenience in driving pleasure 
cars these premises, if they apply, indicate that if for any reason 
a 6 per cent, grade can not be obtained you might just as well 
use a 10 per cent, and that heavy expenditure to get a 7 per cent, 
or an 8 per cent, has no bearing on the convenience of the road. 
This applies only to scenic routes. In the same way for truck 
hauling if you cannot get a 4 per cent, there is no object from 



82 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 




Optional Gearing on Five-ton Model 

The first option is our standard gearing and will be supplied on all orders 
unless otherwise specified. This gearing should be used where the truck 
is to traverse good hard roads at all times, and where the grades do not 
exceed 10 per cent. 

The second option gives great pulling power on the low speeds, and 
the standard speed of 14 miles per hour on high gear. This gearing should 
be used only where the truck has to pull through a very short portion of 
poor road and the great majority of the running is done on direct drive. 
This option is popular with contractors, etc. 

The third option is especially suited for districts where by nature of roads 

(Continued at bottom yage 83). 



GRADES AND ALIGNMENT 83 

the standpoint of convenience in using less than an 8 per cent. 
Other factors, however, apply to reduce this extreme jump as 
discussed later. It should, however, be borne in mind that if 
trucks are operating regularly over a stated route that special 
gear ratios can be and are used to meet the existing grades (see 
Chart C, Note, page 82). Convenience therefore plays a minor 
part in grade selection. 

Mechanical Energy Expended on Plus Grades. — For an equal 
distance between terminals and an equal rise the mechanical energy 
expended on a trailer is not greatly affected hy the rates of grade. 
If, however, the selection of rate of grade affects the distance, but 
not the rise, the lower rate of grade will increase the expenditure of 
mechanical energy. To illustrate: Suppose a tractor is hauling a 
train of farm wagon trailers on a hard surfaced road. The roll- 
ing and grade resistance of the trailers per ton of load can be 
approximated from Table 8, page 76. Suppose there are two 
villages A and B (see Fig. 20) 10,000 ft. apart and 100 ft. different 
in elevation. 

The theoretical energy in foot-pounds per ton of load to haul 
the trailers from A to B is for all practical purposes the same for 
any ordinary maximum grade as shown in Table 9 (page 84) . 

For traffic going from B to A there is some advantage in the 
lower rate of grade. Operation costs on minus grades are 
discussed later. 

If we assume that the fuel consumption is proportional to the 
energy expended, Table 9 indicates that under these conditions 
for a car climbing A to B no appreciable saving in fuel consump- 
tion results from the use of a low grade. This is not strictly 
true when applied to a car carrying the motive power generator 
but it is near enough to help towards a general conclusion. 
It is probable, however, that the time factor makes the lower 
grade somewhat cheaper on which to operate (see discussion of 
time factor, pages 92 to 114). This adds considerable strength 
to the contention that very little practical advantage results from 
reducing grades on local service roads below a reasonable maximum 

or traffic conditions a high speed is undesirable, or in hilly country, where 
the road surfaces are good. This gearing is standard equipment on the 
long wheel base model. 

The fourth option should only be used where the road surfaces are ex- 
ceedingly poor, and the country very hilly. We do not advise using this 
gearing except in extreme cases. 



84 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



where the distance and rise reinain fixed and indicates that the 
use of long straight rates of grade in place of a combination of 
various rates does not materially affect the fuel consumption provided 
the total rise aud fall and distance remains constant. 




V 



-IQ, 000- - 
Fig. 20. 



iS 



100 



J 



Table 9 



Rate of 

grade, 
per cent. 



Resistance Length of 



per ton of 
load, in lbs. 



grade to 
rise 100 ft., 
feet 1 



Foot-lb. of 
energy to 

rise 100 ft. 
on grade 

shown, ft.- 
Ib. 



Remaining 

distance 

on level, 

feet 



Ft. -lb. to 
haul on level 
for the re- 
maining dis- 
tance 



Total ft.- 
Ib. energy 
from A to B 



2K 
4 
5 
6 
8 
10 
Vertical . 



90 


4,000 


120 


2,500 


140 


2,000 


160 


1,666 


200 


1,250 


240 


1,000 


2,000 


100 



Resistance per ton of load on level 40 lb 



360,000 


6,000 


300,000 


7,500 


280,000 


8,000 


266,640 


8,334 


250,000 


8,750 


240,000 


9,000 


200,000 


10,000 



240,000 
300,000 
320,000 
333,360 
350,000 
360,000 
400,000 



600,000 
600,000 
600,000 
600,000 
600,000 
600,000 
600,000 



Now suppose A and B were only 1000 ft. apart in distance and 
100 different in elevation. A road between them on a 10 per 
cent, grade would be only 1000 ft. and would take only 240,000 
ft.-lb. of energy per ton of load on the trailer (see Table 9). A 
road on a 23^^ per cent, grade would have to develop additional 
distance to rise 100 ft. It would be 4000 ft. long and would 
require 360,000 ft.-lb. of energy to haul 1 ton of load. From 
this it is possible to see that where the rise remains fixed and the 
distance depends on the rate of grade the selection of the lower rate 
increases the fuel consumption. Under these conditions it is 
desirable to use the highest rate of grade that will satisfy the 



GRADES AND ALIGNMENT 85 

other requirements of traffic and construction cost such as 
reasonable hmiting loads for teams or trailer trains, convenience 
in the matter of gear shifts and the cheapest construction location 
and maintenance cost (see page 116). 

Effect of Distance Rise and Time on the Cost of Motor Opera- 
tion. — A close analysis of this problem is desirable but hardly 
possible yet. With the great variety of cars, trucks, etc. oper- 
ating under different degrees of efficiency it is hopeless to arrive 
at very definite conclusions. General principles based on the 
laws of mechanics can be derived but actual definite costs are 
another matter which the author frankly leaves to someone in 
the future. Long alternate routes can be advantageously com- 
pared in value for the elements of distance, rise and time but 
the value of a close operating cost analysis of grade hne design 
has a very Hmited apphcation as previously discussed. The 
time element has not much practical value on short trips as we 
all waste considerable time during the day anyway but on com- 
mercial hauhng routes it plays a noticeable part in the cost and 
for this reason we have analyzed some of th,e problems in two 
ways. As a matter of general interest the following approx. 
data is included. This data has been used by the author per- 
sonally for some time but merely as a basis for judgment. 

Cost of General Operation. — We all have heard the cost of 
tires, repairs, gas, etc. talked by the hour for the ordinary pleasure 
car. Each reader probably has his own data but we will assume 
that the total operating cost on hard surfaced roads in 1919 for 
the ordinary passenger car including interest on investment, 
depreciations, insurance, repairs, gas, oil, storage, etc. runs from 
$0.05 to $0.12 per mile. Say $0.08 average, and that of this 
gas and oil cost say $0.02J^, assuming 14 miles per gallon. 

We will assume that 5 ton trucks cost about $28.00 per day 
to operate. That the total cost of operation will run from $0.30 
to $0.50 per mile, on improved roads and will probably average 
about $0.40 per mile. These trucks get about 3 to 5 miles on a 
gallon of gas and the cost of fuel will be assumed at $0.08 per 
mile. 

Two ton trucks under similar service probably cost about 
$20.00 per day to operate or about $0.30 per mile with a fuel 
cost of say $0.05 per mile. 

It can be seen that the cost of fuel is only a small percentage of 
the operation of a truck. 



86 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



Value of Distance Saved on Average Grades Provided Rise is 
not Increased. — Traffic counts, or the general character of 
territory served by the road in question, can be used as a rough 
guide as to the probable proportion of horse traffic, passenger 
cars and trucks. 

Taking the ratios of traffic shown in Table, 2 page 69, for 
the main roads of Massachusetts we get the following average 
value per vehicle for a saving of 1 mile of distance. 



Horse traffic 6 per cent, of total. . . 

Light cars 87 per cent, of total. . . 

Trucks 7 per cent, of total. . . 



6 X 

87 X 

7X 

100 



^0.30 per mile = $ 1.80 
0.08 per mile = 6.96 
0.35 per mile = 2.45 



.1.21 



1.21 



100 



= $0.11 per mile, say $0.10 per mile for the main roads. 



This data agrees with the assumptions of Mr. A. R. Hirst 
given on page 63. For convenience his tabulation is repeated 
at this point. This tabulation assumes average going and does 
not consider various rates of grade. It includes the time factor 
and is intended for the comparison of long routes or Special 
Service Commercial Roads. If used as a basis for estimating 
the value of saving distance on a local service road it is just as 
well to divide the figures by 2. 

Table 10. — Value of a Mile in Highway Distance Saved 
(Based on a car mile operating cost of $0.10) 



Average Number of 
Vehicles per Day 


Saving to Owners 
per Year 


Saving Capitalized 
at 5% equals 


100 


$ 3,650 


' $ 73,000 


250 


9,125 


182,500 


500 


18,250 


365,000 


750 


27,375 


547,500 


1,000 


36,500 


730,000 


2,000 


73,000 


1,460,000 


5,000 


182,500 


3,650,000 


10,000 


365,000 


7,300,000 



Note. — The capitalized value of 1 foot of distance saved for 100 vehicles 
per day equals $14. 

Value of Rise Saved Provided Distance is not Increased and 
the Time Factor is Ignored. — (Cut and Fill Grading Methods). 



GRADES AND ALIGNMENT 87 

The eb'mination of needless rise and fall between terminals 
provided the distance is not increased is evidently valuable. 
There are so many indeterminate factors that we will take refuge 
in simple theoretical mechanics using the simplest data available 
and then modify the results arbitrarily. 

The tabular results given have been used by the author in the 
absence of rehable data as a rough guide in comparing cut and fill 
grade reductions for small changes in rise. They do not consider 
the time factor as it does not have much real practical value for 
short grade changes. Time is, however, very noticeable on long 
steep climbs. For comparing total rise and fall on long routes 
it is better to use Table 11 A, page 91, as this considers the 
time factor. Table 125, page 104, is perhaps more convenient 
for general use and has been modified to meet certain practical 
objections to the more theoretical figures. 

Suppose a farm wagon trailer or an automobile is travelhng 
over a hill, Fig. 21. 



Fig. 21. 

If a car started at A from rest and there was no rolling resist- 
ance, no air resistance, no friction of any kind, no loss of energy 
from the engine running while coasting down the grade from C to 
B or from the application of brakes while descending from C to B, 
the potential energy of the vehicle at the top of the hill C would be 
equal to the energy in foot-pounds required to haul it up the hill 
from A to C and the kinetic energy at B would be the same due to 
its speed developed by coasting. Under these theoretically 
perfect conditions no energy is required to move the load from 
A to B on the level. The energy in foot-pounds per ton of load 
would be 2000 lb. X 100 ft. rise = 200,000 ft.-lb. If the car was 
stopped at B by braking this energy would be lost and the total 
energy expended would have been 200,000 ft.-lb. 

In a similar way the energy expended over the same hill 



88 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

cut down 10 ft. to C would have been 2000 lb. X 90 ft. rise = 
180,000 ft.-lb. 

The saving in energy resulting from cutting down the hill 
10 ft. is 20,000 ft.-lb. or 2000 ft.-lb. per ton of load per foot of 
rise saved provided the car is stopped at B. In case the car is not 
stopped at B and the coasting cars partially climb another hill 
beyond B on their own momentum there is no saving at all 
accomphshed by cutting down the hill shown from C to C as the 
car having a kinetic energy of 200,000 ft.-lb. will go farther 
on its own momentum than the one having a kinetic energy of 
180,000 ft.-lb. 

The introduction of friction and rolHng resistance merely adds 
a constant loss of energy in the normal grade direction which 
is practically the same in amount no matter how much the hill 
is cut down as the difference in the distances ACB, AC'B and AB 
is not appreciable for ordinary road grades. 

As a matter of fact the cars are rarely stopped at the bottom of 
each hill and it is evident that the saving in expended energy due 
to grading down a knoll depends on how much of the potential 
energy at C or C is lost in descending the grades CB or C'B. 
That is, if half the potential is lost through braking an actual 
saving of per ton of load of 1000 ft.-lb. of energy results from 
cutting down the hill 1 ft. If three-fourths of the potential 
energy is wasted a saving of 1500 ft.-lb. results, etc. 

Suppose we carry through a simple case of a farm wagon 
trailer train starting from rest at A. Full power is apphed 
chmbing AC and the energy used per ton of load is (2000 lb. X 
total rise in feet) + (rolHng resistance in pounds per ton of load X 
distance travelled in feet). The potential energy of the train 
at C per ton of load equals 200,000 ft.-lb. in Fig. 19 and the 
energy used in overcoming rolHng resistance is a dead loss and 
equals 40 lb. (rolhng resistance per ton of load from Table 8) X 
distance AC in feet. In a similar way the potential energy at C 
equals 180,000 ft.-lb. per ton of load and the energy lost in 
overcoming the rolling resistance is the same as the first case. 

In descending the hill from C to 5 or C to B practical wastes of 
the potential energy occur through keeping the engine running 
while coasting; through the application of brakes to control the 
speed on steep grades or through throwing the engine into second 
or low gear and keeping it engaged to act as a brake. Rolling 
resistance also eats up its regular supply of energy. On low 



GRADES AND ALIGNMENT 89 

grades no shifting of gears occur as a rule nor is the engine thrown 
out ; the driver merely cuts down his gasoline and takes advantage 
of the gravity help. That is, there is less potential energy wasted 
on a light grade than on a heavy grade. This is the principle we 
wish to develop as it indicates that from a practical standpoint the 
actual saving in operation cost for eliminating a foot in rise and fall 
over a hill is less important on light grades than on heavy grades. 

This adds a certain theoretical strength to the contention 
that for light intermediate grades there is very little advantage to 
traffic through cutting the top of every knoll and filHng every 
hollow. Prof. I. O. Baker developed this same general principle 
in the 3rd edition of his book pubhshed in 1918. 

For purposes of a rough approximation we will assume that 
80 per cent, of the potential energy is lost on a 10 per cent, grade; 
50 per cent, on a 6 per cent, grade and 10 per cent, on grades of 
2 per cent, and less. This is based on Table 8 which shows that 
on a level the rolling resistance per ton on the level is 40 lb. and 
that on a 10 per cent, grade the rolling resistance plus gravity = 
240 lb. per ton. The down hill gravity pull amounts to 200 lb. 
per ton. Forty pounds of this is effective in overcoming rolling 
resistance. We probably lose by brake action 200 — 40 = 
160 lb. or ^^^00 = 80 per cent, plus engine running waste say 
2 per cent. = 82 per cent. This is arbitrarily reduced to 80 
per cent. In a similar way the other two values are derived 
modified by the probability that less brake action and engine loss 
occur on the 6 per cent, grade. Theoretically no loss occurs on 
grades of 2 per cent, or less on the basis of a 40 lb. rolHng re- 
sistance but we have assumed a loss of 10 per cent, as a common 
sense value. The saving of gas on down grade operation is 
extremely variable and depends on the regulation of the minimum 
gas feed and the drivers personal system. These are factors 
which add uncertainty to any figures. 

The theoretical potential energy per foot rise per ton is 2000 
ft.-lb. The loss on these grades may therefore be assumed as 

10 per cent, grade 80 per cent, loss of 2000 ft.-lb. = 1600 ft.-lb. 

6 per cent, grade 50 per cent, loss of 2000 ft.-lb. = 1000 ft.-lb. 

2 per cent, grade or less 10 per cent, loss of 2000 ft.-lb. = 200 ft.-lb. 

If we assume that the rolling resistance of the farm wagon 
trailer on a level road is 40 lb. per ton we can convert the saving 
of energy per foot rise into equivalent distance. 



90 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

1600ft.-lb. 



1 ft. rise on 10 per cent, grade 



40 ft. -lbs. 



40.0 ft. of level distance. 



. . • . 1 lOOOft.-lb. ^ ^ , ,, , ,. 

1 ft. rise on 6 per cent, grade = 77^ = 2o.O ft. of level distance. 



1 ft. rise on 2 per cent, grade = 



40 
200 
40 



= 5.0 ft. of level distance. 



Assuming an average fuel cost for all classes of traffic on the 
road at $ 0.027 per mile on the level the fuel cost per 100 feet 
of rise per car becomes: 

On a 10 per cent, grade v.^^ X $0,027 = $0.02 



On a 6 per cent, grade 
On a 2 per cent, grade 



5280 
2500 
5280 
500 
5280 



X 0.027 = 0.014 



X 0.027 = 0.003 



Using these figures we can compile a table of capitaHzed value 
at 5 per cent, for saving 1 ft. of rise without increasing distance. 
This table has some value as indicating about the extreme 
expenditure that is justified for the elimination of needless rise 
and fall by grading down small hills by cut and fill on Local 

Table 11. — Capitalized Value of Saving 1 Ft. of Rise and Fall 
WITHOUT Increasing Distance 

(Based on fuel cost, per mile per car on a level grade, of $0,027) 
(Time factor not considered) 



Yearlj' saving 



5 per cent, capitalized value 



Average no. of j ' < 

ve 10 es per ay jq ^^^ cent. 6 per cent. 2 per cent. 10 per cent. 6 per cent., 2 per cent. 
grade ' grade or less grade grade 



100 
250 
500 
750 
1,000 

2,000 
3,000 
4,000 
5,000 
10,000 



? 7.55 
18.90 
37.75 
56.65 
75.50 

151.00 
226.50 
302 . 00 
377.50 
755.00 



$ 5.10 


$ 1.10 


12.75 


2.75 


25.50 


5.50 


38.25 


8.25 


15.00 


11.00 


102.00 


22.00 


153 . 00 


33.00 


204.00 


44.00 


255 . 00 


55.00 


510.00 


110.00 



; 151 

378 

755 

1,133 

1,510 

3,020 
4,530 
6,040 
7,5^0 
15,100 



; 102 

255 

510 

765 

1,020 

2,040 
3,060 
4,080 
5,100 
10,200 



I 22 

55 

110 

165 

220 

440 

660 

880 

1,100 

2,200 



Note. — This table can be used as the extreme basis of cut and fill reduc- 
tions on local service roads in order to save fuel alone. If we assume that 
fuel means nothing to 75 per cent, of the traffic divide by 4. 



GRADES AND ALIGNMENT 



91 



Service roads; it does not consider the time factor of operation 
as this does not have much practical bearing on minor changes 
in rise as there is a certain amount of time wasted during the 
day anyway but this factor becomes very noticeable on long 
steep climbs and should be considered in comparing long routes, 
Special Service roads or in making radically different relocations, 
see Table 11 A or 12B. 

Table llA, — Capitalized Value of Saving 1 Ft. of Rise and Fall 
WITHOUT Increasing Distance 

(Based on $0.11 per mile per car total operating cost on a +1 per cent. 

grade) 
(Time factor included see pages 92 to 114 for discussion of time factor) 





Yearly saving 


5 per cent, capitalized yearly saving 


Average no. of 
vehicles per day 


10 per cent. 


6 per cent. 


2 per cent, 
or less 


10 per cent. 


6 per cent. 


2 per cent, 
grades 


100 
250 
500 
750 
1,000 

2,000 
3,000 
4,000 
5,000 
10,000 


$ 21 

52 

105 

158 

210 

420 

630 

840 

1,050 

2,100 


$ 14 

35 

70 

105 

140 

280 
420 
560 
700 
1,400 


$ 3 

7 

15 

23 

30 

60 

90 

120 

150 

300 


$ 427 
1,067 
2,135 
3,202 

4,270 

8 540 
12,810 
17,080 
21,350 

42,700 


$ 275 

687 

1,375 

2,062 

2,750 

5,500 

8,250 

11,000 

13,750 

27,500 


$ 30 

75 

150 

225 

300 

600 

900 

1,200 

1,500 

3,000 



Note. — This table can be used for the comparison of long routes or 
indicates about the maximum allowable expenditure for cut and fill re- 
duction on special service commercial roads. 

Considering the fact that extra fuel and gas means very little to most 
road traffic one-fourth of these values would be a liberal expenditure at 
the present time for such refinements. 



Inefficient Operation. — In order not to lose the sense of value 
of any such figures it is just as well to bear in mind that the 
American public are not particularly careful of small savings. 
The average motor car is not kept in a high state of efficiency. 
If the owner himself does not think it worth while to save 
gasohne by keeping his car in shape how can we expect the 
community at large to make heavy appropriations for construction 



92 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

features of design whose value is based on purely theoretical 
small adcUtional savings. There is undoubtedly more gasohne 
wasted from careless upkeep and dri\'ing than we could ever save 
by the refinements of the most scientific location and for this 
reason the author is not incHned to give anah'ses of this nature 
much weight except as they indicate general principles, namely: 
that the elimination of rise and fall is viore valuable on Special 
Service Commercial roads than an Local Service Roads and of more 
value on steep than on light grades. 

Distance Balanced Against Rise. — ^It is even more difficult 
to analyze such a combination than the simpler cases preceding. 
At present a definite estimate is not possible. With more data 
on motor operation a closer approximation will be possible in the 
future but the gi^eat variety of cars, etc. will probably even then 
tend to weaken the value of the figin-es. In order to show the 
effect of the time factor a simple case will be outhned (Fig. 22). 



Fig. 22. 

Assume two villages A and B 2000 ft. apart separated by a 
hill 100 ft. high with 10 per cent, grades on both sides. Assume 
an operating cost of a truck as S24 per ten hour day or SO. 04 per 
minute exclusive of fuel and oil. Assume the fuel cost as 10.08 
per mile operating on the level. Assume a rolhng resistance of 
40 lb. per ton on the level. 

Under these assiunptions if the truck starts from A and stops 
at B coasting down grade from C to B and stopping at B, the 
energ}^ expended per ton of load would be approximately (1000 
ft. distance X 240 lb. puU) + (an allowance for the engine run- 
ning free from C to B, say 10 per cent, of energ}^ required for 
rimning 1000 ft. on the level or 10 per cent, of 40,000 ft.-lb.) = 
244,000 ft. -lb. 

The amount of energy- required per ton of load from A to B 
on the level would be 2000 ft. distance X 40 lb. pull - 80,000 
ft. -lb. Assuming that the ftiel expenditure is directly pro- 



GRADES AND ALIGNMENT 93 

portional to the expenditure of energy the fuel consumption over 

244 000 
the hill would be QrJnnn ~ ^ times as great as on the level or 

in money at $0.08 per mile on the level it would be ^^o^ X 

$0.08 X 3 = $0.09. The fuel consumption on level = $0.03. 

Suppose we consider the time factor. Assume that the 
maximum speed on the level is regulated by law to 12 miles per 
hour. The time consumed to go 2000 on the level is approxi- 
mately 2 minutes which amounts in money at $24 per day to 
approximately $0.08. Suppose the truck makes 3 miles per 
hour in low gear travelling from A to C and 8 miles per hour 
coasting down hill from C to B. The time over the hill would 
be approximately 5 minutes or in money $0.20. 

The total operating cost over the hill would be approximately 
$0.29 and on the level $0.11 or a difference of $0.18. 

If these assumptions were correct we could afford to increase 
the length of the road to 5300 ft. on the level or 2}i times as 



^% 



far to avoid the hill as far as the operating cost of the truck is 
concerned. These assumptions are not necessarily correct but 
in the absence of more reliable data the author would have no 
hesitation in increasing the distance by from 2 to 23^^ times for 
truck traffic based on such an analysis. The cost of construction 
of the two routes would of course be balanced against the 
operating cost. 

Take the same case for the two villages A and B 4000 ft. 
apart on 5 per cent, grades. 

The energy over the hill per ton of load is assumed as (2000 X 
140) + (10 per cent, of 2000 X 40) = 288,000 ft.-lb. 

The energy on the level = 160,000 ft.-lb. 

Fuel consumption over the hill = $0.11 

Fuel consumption on level = $0.06 

The speed climbing the 5 per cent, grade would probably be 
about 6 miles per hour and about 12 miles per hour coasting down 



94 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

the hill provided the aUgnment is good as the extreme control 
necessary on a 10 per cent, grade is not required. 

The time over the hill becomes approximately 5 minutes 

The time on the level becomes approximately. 4 minutes 

The time cost over the hill approximately $0 . 20 

The time cost on the level approximately 0. 16 

Total cost over hill . 31 

Total cost on level . 22 

In this case we could afford to increase the distance 40 per 
cent, to get a level road from the standpoint of truck operating 
cost. Light motors would not justify any such increase as later 
discussed. 

SfcxISTA ,; _ j^ 

^^ ^ 

S+c( 174 Si-a 19& 

=S+a EOOA 

Plan. 




5fo( 174 



Profile Mam Road 



Sta 196 




Sta 174 



Profile Rclocofion 
Fig. 24. — Pugsley hill relocation. 



S+a^OOA 
=l96Moiin Line 



As discussed on page 89 the value of the reduction of rise 
and fall decreases as the rate of grade decreases so that while in 
extreme cases it is desirable to increase distance to eliminate rise 
this expedient must be used with care for light grades and small 
hills for as a rule short distance outweighs minor intermediate 
rise and fall. 

To give a theoretical apphcation of such figures to a definite 
case we will cite a concrete example known as the Pugsley Hill 
relocation of the Mendon-Pittsford Road in New York State 
(see Fig. 24). 



GRADES AND ALIGNMENT 95 

The main straight road goes, over the top of a high hill; the 
natural saddle is located about 600 ft. west of the main road and 
is 25 ft. lower than the summit on the main road. The main 
road used a 7 per cent, cut and fill grade reduction and the re- 
location a 4 per cent, balanced side hill location. The snow 
conditions are much better on the new location, the cost of con- 
struction is less and the rise less. Suppose we make a rough 
comparison of the cost of operating over the two locations. 

Cost of Operating over Main Line (Trucks) 

, (180 X 1,100) + (10 per cent, of 44,000 ft.-lb.) 

Fuel ^^^ ^^^ , — -— ; X $0.08 per mile on 

212,000 ft.-lb. per mile on level ^ 

level = $0.08 

Time Average 6 miles per hour $0.04 per min. (assumed) = 0. 16 



Total cost $0 . 24 

Cost of Operating over New Line (Trucks) 
(120 X 1,300) + (10 per cent, of 52,000) 

^"^' ^ 212.000 — >< '■'' = » • "« 

Time Average 10 miles per hour (assumed) = 0. 12 



Total cost $0 . 18 

That is we have enough data to conclude that the operating 
cost on the new Une is slightly less than the Old Main Road. 
This data does not however warrant our putting a money value 
on this difference as there are too many unknown factors, 
particularly that of time. Purely as a matter of academic 
interest we can carry this example a little further. This road 
carries today a traffic of approximately 950 motor cars and 80 
trucks per day in summer. It is safe to assume that this amount 
of traffic applied for 250 days per year will about represent the 
total yearly traffic. If we assume that the pleasure cars cost 
about 3^^ as much to operate as the trucks we can arrive at a 
rough guess of the yearly saving $3000. This capitalized at 5 
per cent, would amount to $60,000 which represents theoretically 
the additional amount we would be justified in spending to get 
the new location. 

As a matter of practical interest we will say that despite the 
advantages of an apparently lower operating cost, less snow 
trouble and lower construction cost this new line was not built 
on account of the difficulty of acquiring right of way. The 
farmer wanted $5000 for 3^-^ acres on account of cutting up his 



96 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

property. It was undoubtedly poor policy to let this stand in 
the way and it is probably only a question of time before the 
relocation will be made as this hill controls the maximum grade 
on a through State Route. 

Comparison of Distance and Rise. — For quick rough com- 
parisons of such relocations we can compile a table which in the 
absence of really rehable data will serve the purpose. Table 
12A approximates the theoretical relation. Table 12B is com- 
piled from a practical standpoint. 

We \\dll compute the approximate comparative cost of oper- 
ating on different rates of grade which are close enough to give 
some basis for judgment on the relative value of two locations 
from the standpoint of motor operation. Table 12A gives full 
value to the time factor. Table 12B modifies the fuel and time 
factor. 

Table 12A is made on the basis of $0.11 average motor op- 
eration on a + 1 per cent, grade. This is considered a reasonable 
cost for the proportions of Truck, Car and Horse traffic shown in 
Table 2, page 69. It is assumed that the road ahgnment is 
fairly good; for the effect of dangerous ahgnment see page 141. 
We will assume that the speed is reduced to J^ normal at +5 
per cent, and to }^ normal at +10 per cent, grade; that the 
speed says at normal on the level and remains normal on down 
grades to —5 per cent, and that after this rate of grade is passed 
that it is reduced to }/2 normal at —10 per cent, grade. We 
wiU assume an average fuel cost per mile on the +1 per cent, 
grade of $0.03 and that the fuel consumption is directly pro- 
portional to the theoretical energy expended chmbing. We 
wiU make some arbitrary allowances on down grades. We 
will assume a theoretical draw bar puU of 40 lb. per ton on the 
level. The down grade fuel consumption varies with each driver 
and car. It depends on the minimum gas feed adjustment 
of the throttle and whether the clutch is thrown out and the 
engine stopped or run free; or whether the engine is used as a 
brake and various other factors. The values used by the author 
have been criticised but the suggestions received raise some 
factors or lower others and the net result agrees closely with the 
tabulation. The object of this analysis is to make a start towards 
some reasonable basis for judgment and if the reader believes he 
has better data it is very simple to make up a table similar to 
No. 12 to 12B for use under his conditions. 



GRADES AND ALIGNMENT 97 

On this basis the cost of operation per mile on the different 
grades is as follows: 

Level $0. 107 Level $0. 107 

+ lpercent 0.110 - 1 per cent 0.104 

+ 2percent 0.126 - 2 per cent 0.098 

+ 3percent 0.148 - 3 per cent 0.092 

+ 4 per cent. . 176 - 4 per cent . 086 

+ 5percent 0.210 - 5 per cent 0.083 

+ 6 per cent . 244 - 6 per cent . 095 

+ 7percent 0.278 - 7 per cent 0.107 

+ 8 per cent 0.312 - 8 per cent 0.119 

+ 9 per cent . 346 - 9 per cent . 131 

+ 10 per cent 0.380 -10 per cent 0.143 

These costs were derived as follows. The operating cost of 
$0.11 per mile on a + 1 per cent, grade was apportioned as 
given below: 

Remarks 

Fuel $0. 03 Variable fuel factor. 

Tires . 015 Constant distance factor. 

Repairs 0. 01 ^ Distance, ^ time factor. 

Driver's time 0. 015 Time factor. 

Depreciation 0.02 }i Distance, ^ time factor. 

Interest on investment, in- 
surance, garage, license, etc. . 02 Time factor. 



$0.11 

To determine the operating cost on any other grade we have 
used 3 factors. The constant distance factor made up of tires, 
J^ of the repairs and }^ of the depreciation. The variable fuel 
factor and the variable time factor made up of driver's time, 
interest, M of the depreciation and % of the repairs. This time 
factor is the largest factor. It depends on the speed of the opera- 
tion and is largely a matter of judgment until we have more and 
better information. 

The data given is based on the author's best judgment in 
assigning arbitrary values to these factors and ratios on different 
grades. 

Time cost on a +1 per cent, grade ' $0 . 06 per mile 

Fuel cost on a +1 per cent, grade 0. 03 per mile 

Distance factor cost (constant) . 02 per mile 

Total $0.11 

7 



98 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



Analysis of Relative Operating Cost of Average Motor Traffic for 

1 Mile of Distance on Different Rates of Grade, Based on $0.11 

PER Mile on a 1 Per Cent. Grade 



Distance factor 
$0.02 for 1 per cent, grade 


Fuel factor Time factor 
$0.03 for 1 per cent, grade $0.06 for 1 per cent. 
1 grade 


Total 


Rate grade 
per cent. 


Factor 

ratio for 

each [rate 

of grade 


Cost for 
each 
grade 


Factor ratio 

for each rate 

of grade 


Cost for 
each 
grade 


Factor 
ratio 


Cost for 
each grade 


operating 
cost 


+10 




$0.02 


4 


$0.12 


4.0 


$0.24 


0.380 


+ 9 




0.02 


SVs 


0.11 


3.6 


0.216 


0.346 


+ 8 




9.02 


SVs 


0.10 


3.2 


0.192 


0.312 


+ 7 




0.02 


3.0 


0.09 


2.8 


0.168 


0.278 


+ 6 




0.02 


2ys 


0.08 


2.4 


0.144 


0.244 


+ 5 




0.02 


2M 


0.07 


2.0 


0.120 


0.210 


+ 4 




0.02 


2.0 


0.06 


1.6 


0.096 


0.176 


+ 3 




0.02 


iVs 


0.05 


1.3 


0.078 


0.148 


+ 2 




0.02 


IH 


0.04 


1.1 


0.066 


0.126 


+ 1 




0.02 


1.0 


0.03 


1.0 


0.06 


0.110 


Level 




0.02 


0.9 


0.027 


1.0 


0.06 


0.107 


- 1 




0.02 


0.8 


0.024 


1.0 


0.06 


0.104 


- 2 




0.02 


0.6 


0.018 


1.0 


0.06 


0.098 


- 3 




0.02 


0.4 


0.012 


1.0 


0.06 


0.092 


- 4 




0.02 


0.2 


0.006 


1.0 


0.06 


0.086 


- 5 




0.02 


0.1 


0.003 


1.0 


0.06 


0.083 


- 6 




0.02 


0.1 


0.003 


1.2 


0.072 


0.095 


- 7 




0.02 


0.1 


0.003 


1.4 


0.084 


0.107 


- 8 




0.02 


0.1 


0.003 


1.6 


0.096 


0.119 


- 9 




0.02 


0.1 


0.003 


1.8 


0.108 


0.131 


-10 




0.02 


0.1 


0.003 


2.0 


0.120 


0.143 



Note 1. — If anything the fuel factor between the grades of —3 per 
cent, and — 10 per cent, is a trifle low. 

Note 2. — The time factor between the rates of grade of —5 per cent, and 
— 10 per cent, depends very largely on the alignment, the individual driver 
and whether or not he is in the habit of driving on steep grades. It is 
probably about right for passenger cars but too high for truck operation 
and might be reduced to 1.5 at a —10 per cent, for truck traffic in hilly 
country. 

Note 3. — The time factor on grades of +2 per cent, to +10 per cent, is 
too high for high power touring cars as on good alignment the normal speed 
is often not reduced at all up to 6 per cent. 



GRADES AND ALIGNMENT 



99 



Table 12. — Table of Approximate Capitalized Cost at 5 Per Cent. 

OF Yearly Operating 100 Average Motor Cars Daily for 365 

Days per Year for 1 Foot Distance on the Various Grades 

(Time factor considered) 

(Based on car mile operating cost of $0.11 on average grades) 
(Aligment assumed to be good) 



Rate of 

grade 

per cent. 


Yearly operation 

100 cars daily 

(36,500 cars yearly) 


Capitalized 

yearly 

operation 

cost 


Rate, 
per cent. 


Yearly 


Capitalized 


Level 


$0.74 


$14.80 


Level 


$0.74 


$14.80 


+ 1 


0.76 


15.20 


- 1 


0.72 


14.40 


+ 2 


0.87 


17.40 


- 2 


0.67 


13.50 


+ 3 


1.02 


20.40 


- 3 


0.63 


12.70 


+ 4 


1.22 


24.40 


- 4 


0.60 


11.90 


+ 5 


1.45 


29.10 


- 5 


0.57 


11.50 


+ 6 


1.68 


33.70 


- 6 


0.66 


13.10 


+ 7 


1.92 


38.40 


- 7 


0.74 


14.80 


+ 8 


2.16 


43.20 


- 8 


0.82 


16.50 


+ 9 


2.39 


47.80 


- 9 


0.90 


18.10 


+ 10 


2.62 


52.50 


-10 


0.99 


19.80 



Note. — This table to be used only for general co?nparisons of the relative 
value of routes or alternate locations. The actual costs given are of very little 
value. The figures are based on an average operating cost for all classes 
of travel at $0.11 per mile on a +1 per cent, grade. 

If a car cKmbs a grade going in one direction it will descend 
the same grade going in the opposite direction so that table 12 
can be simplified for purposes of comparing Routes, Alternate 
Locations and Alternate Cut and Fill profiles by averaging the 
plus and minus grades of the same rate. Table 12A is compiled 
on this basis modified shghtly to produce a smooth graph. In 
order to illustrate the relative value of light grades for Truck 
Traffic and Light Motor traffic columns 2 & 3 of table 12 A have 
been compiled modifying the time factor according to the foot 
notes of the operating cost analysis given on page 98. These 
relations are shown by a rough graph, page 101. 

Examples of the Use and Limitations of Table 12A. — The 
main value of this table Hes in the indication of general principles. 
It also affords a quick method of comparison of the value of 
long alternate routes and locations from the standpoint of motor 
operation costs. It has a limited use for the comparison of the 
relative value of alternate cut and fill grade line designs from the 



100 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

standpoint of motor operation but for comparisons of this kind 
Table 12B has more real value. The actual costs given are 
based on personal judgment and must be used with caution. 
The relative costs have a well defined value. 



Table 12A. — Approximate Capitalized Cost at 5 Per Cent, of Oper- 
ating 100 Motor Vehicles Daily (36,500 per Year) for 1 Foot of 
Distance on the Various Grades 
(Time factor included) 



Rate of grade 
per cent. 


Column 1 

Average Traffic 

Trucks & light vehicles 

Based on $0.11 per 

mile average grades 


Column 2 

Light ]\Iotor vehicles 

Based on S0.08 per 

mile average grades 


Column 3 
heavy commercial 

trucks 
Based on SO. 40 per 
mile average grades 


Level 


$14.80 


$10.70 


$54 . 00 


1 


14.80 


10.75 


54.00 


2 


15.10 


10.85 


54.60 


3 


16.10 


11.05 


56.70 


4 


17.90 


11.40 


63.90 


5 


20.50 


12.00 


74.10 


6 


23 . 30 


12.90 


84.50 


7 


26.40 


14.50 


95.00 


8 


29.60 


16.15 


105.60 


9 


32.80 


17.90 


116.20 


10 


36.00 


19.70 


127.00 



Note. — This table to be used only for rough general comparisons of the 
relative value of alternate long routes. The actual costs must be used 
with caution. Alignment good. For effect of dangerous alignment see 
page 141. 

An examination of the graph curves indicates that Hght car 
traffic is not as much affected by rate of grade as heavy truck 
traffic. This is borne out by even casual observation and com- 
mon sense. The hght car curve runs practically level from the 
level rate of grade to 5 per cent, rate and steepens up sharply 
between 5 and 7 per cent, grades. This indicates that for this 
class of traffic there is very httle practical value in the reduction 
of natural profile grades by cut and fill up to a 6 per cent, grade. 
Theoretically the graph indicates a saving in operation costs for 
reductions to about a 2 per cent, rate but this would be an 
excessive refinement at the present stage of highway programs 



GRADES AND ALIGNMENT 



101 



Rate of Orade, ?2r Cent 
01 Z545G789 10 



^130 




254 5GT89I0 
Rc(t(2 of Grade/erCent 

Fig. 25.— Graph of table 12A, showing the relative effect of grade on truck and 
pleasure car traffic (time factor included). This graph assumes that the align- 
ment is fairly good. For the effect of dangerous alignment see page 141 . 

This graph assumes that H the travel is up 'hill and ^ down hill 



102 LOCATIOX. GRADING AXD DRAINAGE OF HIGHWAYS 

and it is rarely economical considering the relative cost of con- 
struction and operation unless the time factor is considered a 
real factor. In a similar way for Commercial Truck Traffic there 
is xery httle practical advantage in reducing the average inter- 
mediate grades by cut and fill below 4 per cent. A reduction to 
2 per cent, is desirable if it can be aecomphshed without excessive 
grading but any such reduction is as a rule not justified except in 
flat coimtry. 

The practical value of Table 12 A and its limitations in sohing 
problems can be illustrated as foUows: 

COMPAKISOX OF AlTEP.XATE LoCATIOXS 

To illustrate the use of Table 12 A for such comparisons we 
will apply it to the two locations over Pugsley Hill given on 
page 94. 

Capitalized Cost of Cpzhatiox for 100 Vehicxjis pee Day 

(Average traffic) 
Main line, 2200 ft. on 7 per cent, grade @ $26.40 = $58,080 

Relocation. 2600 ft. on 4 per cent, grade (^ 17.90 = 46.540 



Appro x imate value of Relocation for 100 vehicles i>er day = $11,540 

(AssTiming tbat time and gasolene means something to every user) 

Capitalize© Cost of Opebatiox (Tight Cabs 100 Datlt) 

Main line, 2200 ft. on 7 per cent, grade @ $14.50 = $31,900 

Relocation. 2600 ft. on 4 per cent, grade @ 11.40 = 29.640 



Approximate value of relocation (100 cars daily) = $ 2,260 
(Ass^jming that time and gas mean something to all these cars) 

Capitaxjzzx* Cost C'tzbatiox (Hzavt Tp.rcKS lOO Datlt, 

Main hne. 2200 ft. on 7 per :--- grade (5 $9o.Chj = $209,000 

Relocations, 2600 ft. on 4 per :-:.:. (5 63.90 = $166,140 



$ 42,860 
Comparison of the r^vo lines from the standpoint of the expenditure of 
Mechanical energy climbing 

1100 lin. ft. X 180 lb. puU per ton = 198,000 ft.-lb. per ton 
1300 lin. ft. X 120 lb. pull per ton = 156.000 ft.-lb. per ton 
All the methods shown an advantage for the relocation. 

This road is a State Route carrv'ing approximately 650 motors 
per day of which approx. iO to 15 per cent, are trucks of over 
two ton eapacity. 



GRADES AND ALIGNMENT 103 

Using the average traffic curve the relocation might possibly 
be worth theoretically 6.50 X $11,540 = $75,000 provided we 
assume that gas and time means something to all the traffic. 
Common sense would, however, forbid any such expenditure on 
this particular line. As a matter of fact the light motor traffic 
would not be particularly benefited as the theoretical saving in 
operation cost is not over 7 per cent. The actual time and 
depreciation saving if any exists is so small that it means nothing 
to this class of traffic. That is, the average hght motor would 
just as soon operate over the hill on a 7 per cent, as to make a 
short detour to get a 4 per cent. We can therefore eliminate 
light traffic operation cost as a factor in the decision. The truck 
traffic is probably actually benefited by the relocation. Theo- 
retically the relocation reduces the operating cost about 20 per 
cent. Some of these trucks are local service trucks and the 
small time saving is of no consequence. Perhaps 50 per cent, of 
trucks get the full theoretical benefit which might justify an 
expenditure of $20,000 for 100 trucks or for this particular road 
carrying about 80 trucks daily a total additional expenditure of 
from $15,000 to $20,000. It should be borne in mind, however, 
that the truck traffic is a small percentage of the total traffic. 
It is not at all likely that the community at large would favor any 
such expenditure for the favored few if they knew what was going 
on and it is not likely that if the proposition was put up to the 
truck owners that they would be willing to plank down $20,000 
for the work. 

The argument for this location therefore boils down to the facts 
that while we know that the relocation is the better line from the 
standpoint of operation we would hesitate to spend much addi- 
tional at this time as the road program is financed by a general 
tax and the direct return to the community at large is too in- 
tangible. If we were working on a reconstruction program 
financed by motor license fees of which the truck owners paid a 
reasonable proportion of the cost there would be no hesitation in 
building the line as it could be done for a sum well within the 
amount saved. 

The use of Table 12 A may not warrant placing a money valv^e 
on the saving in operating cost hut it certainly justifies the con- 
clusion that the relocation is the better line from the standpoint of 
motor operation. If such a relocation improves snow conditions, 
increases the convenience by preventing gear shifts, reduces the 



104 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



rate of maximum grade for a long road and can be built for less 
than the old road location, which was the case in this instance, 
it is most certainly justified. 

Practical Basis of Comparison of Short Alternate Locations 
and Cut and Fill Profiles. — For the benefit of the younger men, 
Table 12B has been compiled to serve as a basis for arriving at 
the extreme expenditure justified by savings in operation costs 
due to relocations and grading at this time 1920. Bearing in 
mind the approximate nature of such figures, no change in loca- 
tion or profile design should be made unless the saving in opera- 
tion cost is distinctly larger than the increase in construction 
cost. A ratio or at least 2 to 1 is recommended. 

Column 1 applies to Local Service Roads and Secondary State 
Routes carrying up to approximately 1800 vehicles per day. 

Table 12B. — Approximate Capitalized Cost at 5 Per Cent, of Oper- 
ating 100 Motor Vehicles Daily (36,500 per Year) for 1 Ft. of 
Distance on the Various Grades 

Note. — Time factor modified Columns 1 & 2. Fuel cost not con- 
sidered for 50 per cent, of light motors Columns 1 & 2. 



Rate of grade 
per cent. 


Column 1. 

Local service roads 

and secondary state 

routes 


Column 2. 

Main inter-city state 

roads 

Probable future traffic 

1800 or more 


Column 3. 

Future commercial 

truck toll roads 


Level 


$ 9.10 


S12.20 


$54.00 


1 


9.10 


12.20 


54.00 


2 


9.15 


12.30 


54.60 


3 


9.25 


12.50 


56.70 ■ 


4 


9.40 


12.80 


63.90 


5 


9.70 


13.50 


74.10 


6 


10.20 


14.50 


84.50 


7 


11.20 


15.80 


95.00 


8 


12.50 


17.70 


105.60 


9 


14.00 


19.80 


116.20 


10 


15.50 


22.00 


127.00 



Note. — As a general rule make no changes in existing locations or grade 
lines which fit the natural surface unless the saving in approximate operat- 
ing cost is at least twice the additional cost of construction. This note does 
not apply to changes which are desirable to improve the safety or con- 
venience of the road. 



GRADES AND ALIGNMENT 



105 



Rate ofGrade, Per Cent 

I 54 567 89 10 




E. 


<y 


o 


E_ 


KJ 


lO 


0) 


o 


4- 


<-> 


o 


r 


t 


^ 


o 


o 


\ 


c:> 


c 


iT) 


£1- 


VO- 


< 


rO 



40 



50 



note: 

Ti'm(? facformbolifiecl Curves !» 2 
Fuel cost not cons ic^erec^ for SO % 
~of light- motors Curves la 2 



CURVENQ.2 

MiPiin InfercitLj - 
State Roads. 
Prct^or Me Future 



40 



Z^—and 



10 



L oeal Service l?<?aGls 

Secondary 
State Roads. 



Traffic 1800 or More 




50 



20 



Z34 56789 10 
Rate of Grade^PerCent 

Fig. 26. — Graph of table 12B. A practical basis of comparison. This graph 
assumes that the alignment is fairly good, (see also page 141). 
This graph assumes that Ji the travel is up hill and Y^ down hill. 



106 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Column 2 applies to Main inter-city Routes. Column 3 indicates 
possible expenditures, sometime in the future, for Special 
Truck hauling roads constructed and maintained by a direct 
tax or toll on the trucks using the road. 

Examples of the Value and Limitations of Table 12B. — These 
examples are included as much to show various practical con- 
siderations in grade Une designing as they are to illustrate the 
general value of Table 12B. No rules or standards can be used 
without judgment. 

Case I. Comparison of Short Alternate Locations (Distance 

Balanced Against Rise) 

Use the Pugsley Hill relocation described on page 94. A 
practical comparison of value of the two Knes is not entirely 
based on the relative operating and construction costs. 

Suppose we compare this relocation assuming that this road 
might be either a Local Service Road carrying 500 motors per 
day; a State Inter-city Route carrying 2000 motors per day or a 
Future Commercial Truck Road carrying 2000 trucks per day. 

Use Table 12B, columns 1, 2 and 3. 

Local Service Classification 

Existing road location, 2200 ft. on 7 per cent, grade @ S11.20 = $24,640 

New location, 2600 ft. on 4 per cent, grade @ 9.40 = 24,440 

Approx. advantage of Relocation per 100 vehicles = 200 

Total advantage for this case, 5 X $200 =$ 1,000 

From the standpoint of operating cost this relocation can be 

assumed to warrant an additional expenditure of — -— = $500. 

ij 

For a local service road the saving in operation cost is negligible 
(not over 1 per cent.). As a matter of fact the approximate 
nature of the figures makes it doubtful if there is any saving. As 
previously stated page 103 the relocation was warranted by im- 
provements in snow conditions, reduction of maximum grade for 
a long road and a reduction in construction cost. 

Inter-city Road Classification 

Existing location, 2200 ft. on 7 per cent, grade @ $15.80 = $34,760 

Relocation, 2600 ft. on 4 per cent, grade @ 12.80 = 33,280 

Approximate value Relocation per 100 motors = 1,480 

Total advantage for this case, 20 X $1480 = 29,600 

$30000 
Allowable expenditure = $15,000 

Under these conditions the relocation is desirable. 



GRADES AND ALIGNMENT 
Future Truck Road Classification 



107 



(Construction financed by road users) 

Existing location, 2200 ft. on 7 per cent. @ $95.00 = $209,000 

Relocation, 2600 ft. on 4 per cent. @ 63.90 166,140 

Approximate value of relocation 100 trucks = 43,000 

Total advantage for this case, 20 X $43,000 = 860,000 

Approximate allowable expenditure = $500,000. 

For a road of this character the relocation would not only be 
justified but a further reduction to a 2 per cent, grade by cut 
and fill could probably be made at a cost of only a fraction of 
$500,000. 

Comparison of Cut and Fill Grade Line Profiles. — ^In comparing 
all alternate cut and fill grade fines it is assumed that the road 
is well located or that it is fixed for some practical reason by 
existing rights of way. 

Case I. Comparison of the Use of a Reasonable Maximum Grade 

AND a Reduction in Total Rise with a Lower Rate of Grade 

AND No Reduction in Rise. (Distance Fixed) 





45, 




THESE AREAS EQUAL 














■'"'Level Grade-' 


^ 




''T? 

^ 




;5 












Om 


dc 


^ 




0^ 












<Vl 










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'^'^ 


— 


"■«<" 


- 




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1 


■^ 


>^ 




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v? 


TT777 





( 




'• 


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e. 


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i 6 




f 


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11 12 



Stations 
Fig. 27. 



Grade line ''A" uses a 5 per cent, maximum and decreases the 
height of the hill 9 feet. 

Grade line ''B" uses a 4 per cent, rate and does not reduce the 
height of the hill. 

The Amount of Excavation is the Same for Both Lines. — For 
a given expenditure of money in rolling topography is it better 
to use a reasonable maximum and reduce rise or use a lower rate 
of grade and fail to reduce rise? 

Suppose we compare this line first from the standpoint of the 
mechanical energy required for climbing from Sta. 9 + 24 to 
2 + 00. 



108 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Energy Expended 
Grade Line A 

400 ft. on 5 per cent. Grade @ 140 lb. per ton = 56,000 ft.-lb. 
324 ft. on Level @ 40 lb. per ton = 12,960 ft.-lb. 

Total = 68,960 ft.-lb. 

Grade Line B 

724 ft. on 4 per cent. Grade @ 120 lb. = 86,880 ft.-lb. 

The expenditure of energy on the down grade is indefinite 
and is due very largely to the driver. He may coast and let bis 
engine run free or use the minimum gasolene and use the engine 
as a break. The chances are that he will use slightly less on 
Grade B than on Grade A but not enough less to balance the 
advantage of Grade A on the cHmb. The probabilities are all 
in favor of the supposition that Grade A is the best grade on the 
score of fuel consumption. 

Now suppose we use Table 12B to compare these two lines. 
This table considers the indefinite items of down grade operation 
and wear and tear on the car. 

Compare the operating cost on these two profiles. Use column 
I Table 12B. Local Service Roads. 

Grade "B" 724 ft. on 4 per cent, grade @ $9.40 = $6805 

Pr-o^o '' A " / 400 ^*- on -5 per cent, grade @ $9.70 \ _ 
Grade A ^ ^^^ ^^ ^^ ^^^^^ ^ ^^^ j - 6828 

These figures indicate that for all practical purposes the cost 
of operation is the same for either Grade A or Grade B, and that 
either could properly be used depending on which fitted the 
topographical conditions best. The author believes this is a 
sound conclusion. 

On local service roads the evidence is sHghtly in favor of grade 
line A and as time and car depreciation have less real value than 
on Commercial Roads. It is assumed that this hill does not 
control the maximum grade and that 5 per cent, is reasonable 
for this road. Even on Commercial roads it would probably be 
better to use grade line A if this hill did not control the maximum 
grade but if it did control the maximum grade there is absolutely 
no question but that grade line B is the better design. 

Case II. To Compare Different Depths of Cutting Through the 

Top of a Hill 

The profile of the Scottsville-West Henrietta Road shown, is a 
portion of a road now under contract. The maximum grade on 



GRADES AND ALIGNMENT 



109 



this road is 7 per cent. The two 5 per cent, grades and vertical 
curve marked ''A" show the plan grade. 

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The question is whether it is desirable from the standpoint of 
operating cost to cut this hill any farther by grade line "B" and 



110 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

how much of a cut is justified according to Table 12B. This road 
is a local service road carrying approximately 250 motors per 
day. It is a crossroad in the system shown in Fig. 13, page 41 
and its improvement will not probably increase the traffic to 
over 400 rigs per day. 

Vertical curve ''A" has a length of 300 feet. Suppose we try 
a 400 foot vertical curve; this would cut down the hill approxi- 
mately 1.25 feet below Curve "A.^' The relative cost of operat- 
ing over grade ''A" and grade ''B" from station 176 to 181 by 
Table 12B is as follows (Column I). 

^ J T ,, . „ / 200 ft. on 5 per cent, grade @ $9.70 \ ^ .___ 
Gradelme ''A'M „„„ ,, ^-..^ , * /^ n on r =$4700 

I 300 ft. on 23-^ per cent, average @ 9.20 J 

,/ 100 ft. on 5 per cent, grade @ 9.70 \ 
Grade line B < .^^ j, ^i/ + z;^ n on f = $4650 

I 400 ft. on 2)4 per cent. @ 9.20 J 

Approximate advantage line ''B" for 100 motors per day = $ 50 

Total advantage, 4 X $50 = $200 

Approximate allowable expenditure = 200 

= $100 

2 

The excavation taken from the top of the hill will not affect 
the height of the grade Station 190 and 203 so that the cut of 
1.25 feet represents the full value of this work. 

The extra cost of grade line '^B" over grade Hne ''A" would 
be about $350 which indicates that the plan grade should not be 
lowered. If this road carried 1500 motors per day we might be 
justified in grade Hne ^^B" from the standpoint of operation cost 
but practically it would probably not be used first on account of 
damaging existing property needlessly and second because 
reducing this hill one foot in elevation would be an excessive 
refinement with no practical advantage. If the figures had indi- 
cated a cut of 4 or 5 feet some weight might be given to the data. 

Now suppose we consider this profile from the standpoint of 
a Future Truck Road carrying 2000 trucks per day. Use Column 
3, Table 12B. 




This hill is a 5 per cent. hill. The capitalized value of cutting 
1 ft. off from this hill per 100 trucks daily can be assumed roughly 



GRADES AND ALIGNMENT 111 

as the difference between the capitahzed operating cost on 40 
feet of 5 per cent, grade and 40 feet of level grade. Using Column 
3 Table 12B, this gives: 

40 ft. on 5 per cent, grade @ $74.10 = $2964 
40 ft. on level @ 54.00 = 2160 

Value per 100 trucks daily = $ 800 approximately. 

For 2000 trucks the total value = $16,000 per ft. cut. 

This indicates that we can cut this hill down any amount we 
wish. 

Suppose we try a level grade ''C" using a 30-ft. cut and 20-ft. 
fill. The rough value of this work from Stations 171 to 190 is 
approximately as follows. 

Grade line ''C" 1900 ft. on level @ $54 = $102,000 

Grade line "A" / ^^^^ ^^' "^^ ^ P^' ''^^*- ® ^^^'^^ \ - 128 000 

Urade ime A ^ ^^^ ^^ ^^ average 2^ per cent. @ $55.60 / " ^^^'""" 

Advantage of grade line "C" per 100 trucks daily = 26,000 

Total advantage, 20 X $26,000 = $520,000 

The hill could be cut down to grade hne '' C " for about $60,000. 
Even however, for a road of this character the hill would not be 
cut down below grade line "D" based on a 2 per cent, grade as 
2 per cent, is about the minimum required from the standpoint 
of cheap operation. 

It can be readily seen that if roads of this kind are constructed 
they should be removed from the existing highways except in flat 
country as the deep cuts and high fills would make abutting 
properties inaccessible and any such grade line would raise 
right of way costs along existing roads way above entire new 
locations. It is also certain that existing roads rarely meet the 
requirements of engineering location that a road of this kind 
would demand. 

If anyone seriously attempted to apply a truck operation cost 
analysis carried to its logical conclusion on the usual roads of 
today he would merely discredit bis judgment (see page 60). 

Case 3. Comparison of a Uniform Rate Less than the Maximum 
WITH A Combination of Rates None of Which Exceed the Maxi- 
mum (Distance and Rise Fixed) 

From the standpoint of expenditure of mechanical energy 
climbing there is no difference in grade hnes ''A" and ''B " (figure 
29 page 112). 



112 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



For short grades of this nature the elements of time and wear 
and tear on a car are more theoretical than practical. Table 
12B gives some weight to these factors. 



Uniform 4 % ^ 
Grade Lme "B'' 



f^dfuralj/^ 




Fig. 29. 

OOMPARISON OF GrADE LixES "A" AND "B" 

Table 12B. — ^Local Service Road Column I 



Grade line "A " / ^^^ ^^- ""^ ^ P^' ^^^^- ® ^^'^^ ^ 
Orade line A <^ ^00 ft. on 3 per cent. @ S9.25 / 

Grade line "5" 400 ft. on 4 per cent @ S9.40 
• Advantage of Uniform Rate per 100 vehicles 
Approx. allowable expenditure per 100 vehicles 



= S3790 

= S3760 
= 830 
= $15 



The extra cost of the uniform 4 per cent. (Grade hne '^B") 
over grade Hne '^A" is approximately S125 so that this road 
would have to carry at least 800 rings per day to justify this 
expenditure. This volume of traffic is more than most local 
service roads carry. 

As the rates of grade are reduced the value of smootliing out 
the profile becomes less so that even on main intercity routes no 
advantage, either theoretical or practical results from laying 
such a profile for rates less than 3 per cent. 

The practical conclusion to be drawn seems to be that for 
Local Service or Secondary State Routes in thinly settled 
territory no expenditure is justified on such profile refinements. 

On main inter-city routes on which the cities are located closer 
than 100 miles some expenditure on such reductions is allowable 
as the grades approach the maximum but they should not exceed 
the amounts indicated by column 2, Table 12B, as modified 
by the footnote. Even on such roads there is no advantage in 
smoothing out grades of less than 3 per cent. rate. 

It is also well to bear in mind that the length of a gi^ade and 
its location has a distinct bearing on its effect on traffic. That is, 
a short 7 per cent, grade 200 ft. to 300 ft. long located at the 
bottom of a long 5 per cent, grade does not in a practical way 



GRADES AND ALIGNMENT ll3 

affect the operating cost for single unit motors^ as the speed of 
the cars is generally increased above normal on approaching such 
a hill and the momentum is effective in partially overcoming the 
increase in rate. Such a profile can be approximated as a uni- 
form 5 per cent. If located at the top of such a hill the difference 
in rate is noticeable. 

The figures given in Table 12B represent the extreme expendi- 
ture allowable and in using them to check a profile design no 
change should be made in the plan grade unless they show a 
distinct advantage in operating cost over the additional cost of 
grading. 

SUMMARY OF MOTOR TRAFFIC CONSIDERATIONS 

From a practical standpoint the following general conclusions 
seem sound: 

1. The selection of maximum grade within the bounds of standard prac- 
tice is not affected by the ability of single unit motor vehicles to climb. The 
long trailer train system demands low rates of ruling grade. 

2. The selection of maximum grade within the bounds of standard 
practice is not affected by the factor of safe descent from the standpoint of 
single unit motors provided the ahgnment is safe. 

3. For a fixed rise and fall and distance a combination of different rates 
of grade have no appreciable effect on fuel consumption. However, the 
total cost of motor operation including the time factor is probably slightly 
less for a uniform grade. This effect is not however noticeable enough 
to reduce the steepest grade below a reasonable maximum and has no prac- 
tical effect on the use of rolling grades on intermediate profile design as the 
value of smoothing out minor grade irregularities becomes less as the rate of 
grade is reduced. 

4. For a fixed rise and variable distance depending on the rate of grade, 
the lower the rate of grade the higher the fuel consumption and operating 
cost. Under these conditions the grade should be kept to the steepest 
reasonable rate. 

5. In the matter of convenience in driving it is desirable to avoid shift- 
ing gears. The limiting rates of grade at which gears are shifted for the 
ordinary car on improved roads is about 6 and 10 per cent, for pleasure 
cars, and 5 and 8 per cent, for Standard Trucks. This however is subject 
to constant change and is not of much importance. 

6. The value of distance saved can be closely approximated. 

7. The value of rise saved can not be closely figured but it is certain 
that it has more money value on steep grades than on light grades. 

8. In locating roads, distance can be balanced against rise but it is not 
possible to analyze this closely and as a rule distance should rarely be in- 
creased particularly if good alignment is lost unless it is necessary to get a 

1 By single unit motors are meant trucks without trailers. 
8 



114 LOCATIOX. GRADING AXD DRAIXAGE OF HIGHWAYS 

reasonable maxiniuin grade or unless a noticeable locali2ed rise and fall can 
be eliminated by a short additional distance. (Use Table No. 12B page 
104 for comparisons of this nature.) 

9. Ruling grades need not be consistent in rate as far as ordinary motor 
traffic is concerned as they do not limit the load of single unit hauling rigs. 
Ruling grades should be consistent if the trailer train system controls the 
design. 

It can be seen that the requii-ements of ordinary' motor traffic 
have less definite claims for consideration in reducing the rate 
of max' . ■'. : j.de^ than Horse Traffic but have more claim than 
horse traffic in the matter of reducing distance and rise and fall 
on account of the large amounts of money annually spent on 
operation costs. Summarizing we can say that orchnar%- motor 
traffic wan-ants higher rates of maximum grades than horse 
traffic but demands short clLstance and less rise and faU on steep 
grades. The reduction of rise and faU on light grades is of very 
Uttle practical value. For certain special conchtions where the 
trailer train must be considered, maximum grades may weU be 
reduced below even the limits reciuired for horse traffic. 

Effect of Maintenance Cost on the Selection of Maximum 
Grades. — The maintenance of shoulders, ditches, and water- 
bound macadam, gravel or natural soil surfaces increases in cost 
rapidly on grades over 5 per cent. From the standpoint of 
^laintenance cost 5 per cent, is the logical maximum rate. 

Effect of Safe Footing on Maximum Grade. — In regard to the 
matter of safe team footing, it is possible to select some t^-pe 
of pavement which wiU satisfy this condition for any gi'ade used 
but a change in surfacing to meet this requirement is often omitted 
on account of expense and more often omitted by careless design. 
!Most of the rigid pavement t}-pes give satisfactory- footing up to 
5 per cent, which is the practical limit without special design. 
Bituminous macadams can, by variations in manipulation, be 
made suitable for gi'ades up to 8 per cent. Plain macadams give 
good footing for any grade but are expensive to maintain over 5 
per cent. From the standpoint of team footing .5 per cent, has 
a distiQct advantage on main roads where rigid t^-pes are desir- 
able, and 7 or 8 per cent, is a reasonable Umit on side roads where 
some form of macadam or gravel will probabh' be used. Team 
footing is however, becoming less important as a decichng factor. 

Effect of Farm Hauling on Maximum Grade.— From the stand- 
point of accommodating ordinaiy farm team loads 7 per cent, is 



GRADES AND ALIGNMENT 



115 



the logical ruling rate. This is based on a load of 5000 pounds 
for farm hauling which includes wagon weight. The records 
of produce dealers in the Eastern States show that the ordinary 
wagon weighs about 1350 lb. and that 3500 lb. is a large net 
load. This load of 2.4 tons corresponds with the maximum 
theoretical load for 7 per cent, hard surfaced grade. Team 
loads of six tons would be very unusual which means that the 
ideal teaming grade of 23-^ per cent, need not be considered except 
in level country where it can be obtained without much extra 
cost. 

Effect of Construction Cost on Maximum Grade. — From the 
standpoint of construction cost 5 to 7 per cent, can generally 
be built without excessive expenditure even in hilly country. 

Maximum Grades in Present Use. — The maximum grades in 
present use represent the best judgment of engineers from all 
over the w^orld backed by practical experience and traffic tests 
of generations. It is true that they are largely based on factors 
of horse traffic, reasonable construction and maintenance costs 
but the author beheves that these factors are still the most 
important deciding elements in the selection of maximum grade 
for most roads. The following Table 13 gives the rates in 
common use and is probably the most reliable basis for design 
that can be used. 



Table 13. — Maximum Grades in Foreign Countries 



Location 


Mountainous 
districts, 
per cent. 


Hilly 
districts, 
per cent. 


Level 
districts, 
per cent. 


Prussia 

Hanover 

Baden 

Brunswick 


5 

4 
8 

6 


4 

3M 
6 
4 
3>^ 


2K 

5 
3 


Holyrod Road in England 





Military highway over the Alps — Italian side, 4,1^ per cent., Swiss side, 
6 per cent. 



Location 



National roads. Departmental 
per cent. roads, per cent. 



Subordinate 
roads, per cent. 



France . 



116 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 
Maximum Grades in the United States 



State 


Main roads, 
per cent. 


Side roads, 
per cent. 


Unusual cases, 
per cent. 


New York 

Massachusetts 

Connecticut 

New Jersey 


5 
5 
5 
5 

6 

5 and 6 

5 

6 


7 and 8 
7 

6 and 7 
5 


n 

Q 


Michigan 

Missouri 

Washington 

Illinois 


9 



United States National Forest Roads (Mountainous Districts) 

1st class roads Long grades 5 per cent. — short grades 7 per cent. 

2d class roads Long grades 7 per cent. — short grades 10 per cent. 

3d class roads Long grades 10 per cent. — short grades 12 per cent. 

State of Colorado (main mountain roads) 6 per cent. 

Recommended Practice Maximimi Grade Design. — From the 

standpoints of horse traffic, single unit motor traffic or trucks 
with one trailer, safe footing and economy of construction and 
maintenance the following recommended rates of maximum 
grades will give moderately good satisfaction. In unusual cases 
the possibiHty of the extensive use of long trailer trains would 
tend to reduce these recommended rates but the author wishes 
to emphasize the opinion that very few roads need be designed 
at this time primarily for long trailer trains. The following rates 
are satisfactory for the ordinary motor equipment used by the 
great majority of road users and additional expenditure would not 
be warranted for the benefit of a few men. For the effect of 
dangerous alignment on maximum grade see page 140. 

Main Commercial Roads in Flat Country. — ^Long 2 per cent, ruling grades 
are desirable but do not justify much additional construction cost. Any 
long ruling grade up to 5 per cent, will probably be satisfactory. Short 6 
per cent, are not inconsistent. A large volume of hauling by trailer trains 
might warrant reductions below usual practice provided the interests operat- 
ing such haulage paid the increased cost of construction. 

Main Commercial Roads in Hilly Country {Well Settled Districts). — ^Long 

5 per cent, ruling grades are desirable and justify considerable expenditure 
provided they do not increase the total distance. Seven per cent, grades 
are probably justified to prevent increase in distance for a fixed rise. Long 

6 per cent, grades are fairly satisfactory but as a rule if 5 per cent, cannot 
be reasonably obtained it is just as well to jump to 7 per cent. Short 7 



GRADES AND ALIGNMENT 117 

or 8 per cent, grades are not inconsistent in connection with, long 5 per cent. 
and 6 per cent, grades provided the element of safe team footing is considered. 

Main Roads Pioneer Districts. — ^Long 5 per cent, grades are very desirable 
provided they do not increase the total distance particularly if the road is 
a natural soil road and considerable horse traffic prevails. Any long grade 
up to 7 per cent, is fairly satisfactory. Short 7 and 10 per cent, grades are 
not inconsistent except for trailer trains. Grades higher than 7 per cent, 
are not, however, in much favor on account of danger and high maintenance 
cost. 

Side Agricultural Roads or Unimportant Pioneer Roads. — Any long grade 
up to 7 per cent, is satisfactory. Short 10 per cent, grades are consistent 
in connection with a 7 per cent, ruling provided the element of safe footing 
is considered. Grades steeper than 7 per cent., however, have a high 
maintenance cost. 

Scenic Roads. — ^Long 6 per cent, grades are convenient on account of 
preventing gear shifts. Ten per cent, is not unreasonable for such roads 
except that on a 10 per cent, grade the alignment should be easy as later 
discussed and the maintenance cost is high. 

Effect of Alignment. — Sharp curves affect steep grades as 
taken up under the subject of Alignment (see page 138) « 

Unusually High Rates of Grade. — Grades as high as 11 per 
cent, have been constructed on State improved roads in New 
York and as high as 9 per cent, in New Jersey and Illinois but 
the general opinion of the departments under which these grades 
were built is that they would not again use such a high rate 
except in villages where any material change in street elevation 
would damage valuable properties. Outside of corporations 
it is bad practice to use long grades of greater rate than 7 per 
cent, for if any road is of sufficient importance to warrant engi- 
neering plans for the future it is certainly of sufficient importance 
to warrant a reduction in grade to a reasonable rate. 

Consistent Maximum Grades. — The design should be con- 
sistent if horse traffic is considered. Take for example a road 
between two shipping points. It is first necessary to determine 
the portion tributary to each terminal and then the practical 
grades on all the hills on each portion in order to decide what 
consistent ruling grade can be adopted without excessive cost. 
There is no object in reducing a hill from 7 to 5 per cent, pro- 
vided the total rise remains fixed with a large expenditure if 
nearer the terminal there is a grade that cannot be reduced 
below 7 per cent. It should be borne in mind, however, that 
the nearer you approach the shipping or market point, the 
more traffic the road will have, and if the hills are naturally 



118 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

flatter the ruling grade should be reduced. The direction of 
heavy traffic on each hill should be determined and considered. 
Ordinary motor traffic does not require consistent maximum 
grades but the trailer train method does require them. Consider- 
able expenditure is justified to obtain consistent grades for the 
benefit of team hauhng on local service roads. 

Effect of Maximum Grade on Cost. — Money spent on the 
reduction of maximum grade is never wasted unless distance is 
increased for a fixed rise by a grade lower than a reasonable 
maximum. It is not good pohcy to spend large sums to reduce 
below 5 per cent, in hilly country or 2 per cent, in level country 
even where distance is not increased. The effect on cost of the 
selection of a 5 per cent, in place of a 6 per cent, or a 6 per cent, 
in place of a 7 per cent, depends largely on the method of con- 




FiG. 30. 

struction that must be used. Where locations are fixed by well 
estabhshed right-of-ways and permanent structures and the cost 
of new right-of-way is very high grades are generally reduced by 
cut and fill. Under these conditions the effect of the selection 
of rate is very marked and no general relation can be established 
as each case is a law unto itself. To show the fluctuating 
amounts of excavation per mile for different improvements 
based on different rates of ruling grade where cut and fill was 
used, Table 14, page 120, has been compiled. 

Unfortunately many of the roads in the older states were not 
laid out on natural engineering locations and grade improve- 
ments are expensive either on account of excessive cut and fiU or 
the high cost of new right-of-way on a better location. In 
mountain road or ordinary locations in newly settled districts the 
question of right-of-way rarely handicaps the design and easy 
grades are obtained at moderate cost by natural locations which 
avoid steep adverse grades by going around a hill or develop 
moderate grades on a long climb by a longer distance. In 



GRADES AND ALIGNMENT 



119 



climbing on a sidehill location the road section is generally what 
is known as a balanced section, that is, the cut just makes the 
fill by side displacement. The amount of excavation per mile 
is not affected by the rate of grade but sometimes the length of 
road is affected. 

GeneraHzing we can say that the effect of grade reduction on 
cost is not as marked as for cut and fill methods and that roughly 
the relation of cost to grade depends on the length which is 




Fig. 31. — Balanced side hill section. 



often inversely proportional to the rate; that is, where cut and 
fill is used a 5 per cent, grade might easily cost three or four times 
as much as a 6 per cent, grade but where sidehill location is 
possible a 5 per cent, would rarely cost more than % as much as a 
6 per cent. This is of course affected by all sorts of local conditions 
and may not apply at all but is true by and large and serves to 
illustrate the relation of rate to cost. To illustrate (fig. 32) : If 
the difference in elevation between A and B is 1000 feet a 6 per 
cent, grade would require approximately 33 ^3 miles of length and a 



120 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

5 per cent, grade 4 miles to make the ascent. If the direct dis- 
tance between .-1 and B is less than 3J^ miles the lengths of the two 
lines will be approximately as given. If the distance from A to B 
is more than 4 miles there would be Httle difference in the leno-th 

as it would merely mean that the 5 per cent, started to chmb 

' B Elevafion 6000 





Fig. .32. 

sooner than the 6 per cent. Under most concUtions the cost 
would be more affected by the character of the excavation on the 
different locations and by the number of switchbacks required 
for the smaller rate. The difference in cost due to the difference 
in rate of maximum grade in mountain location does not often 
XL-arrant the adoption of excessive grades. 

Table 14. — Compiued from the 1908 axd 1909 Reports of the Xew 
Jersey Highway Commissiox 



Name of road 



Length 

in 

miles 



Maxunum 

original 

grade, 

per cent. 


Maximum 
improved 

grade, 
per cent. 


Excavation in 
cu. 5"d. per mile 


7.0 


3.2 


2.220 


S.o 


o.O 


4. 680 


5.2 


4.5 


2.. 500 


8.0 


2.8 


8.200 


13.0 


6.5 


5,200 


2.8 


2.S 


540 


4.5 


2.9 


6.500 


2.5 


2.0 


3.200 


4.2 


2.0 


1.700 


12.5 


.5.0 


4.100 


6.0 


3.9 


2,000 


Level 


Level 


(Emb.) 50.000 


12.0 


6.5 


5.700 


6.7 


4.0 


5.200 


6.4 


3.7 


3.500 


3.4 


1.1 


5.000 


3.4 


1.4 


4.500 


4.1 


1.6 


8.100 


7.6 


5.0 


3.800 



May's Landing 14.0 

Eivervale 5.0 

Westwood 1.2 

Franklin Turnpike 1.6 

Summit 1.9 

Lamberton 3.9 

Westfield 3.1 

Blue Anchor 2.3 

Malaga 5.7 

Whitehouse 6.5 

English Creek ; 6.7 

Paterson Plank Road ' 2.3 

Yesler Wav 2.7 

Camden 2.4 

Evesham 2.4 

ScheUenger's Landing 2.1 

Goshen ' 2.6 

Tuckahoe 4.3 

Hopewell 2.0 



GRADES AND ALIGNMENT 



121 



Table 14. — Compiled from the Records of the New York State 

Highway Commission 
Plans for 1911 



Name of road 



Character 
of country 



Maximum 
improved 

grade, 
per cent. 



Width of 

section 

between 

ditches, 

ft. 



Exc. in 
cu. yd. 
per mi. 



Pittsford — North Henrietta 

Indian Falls — Corfu 

Pembroke — East Pembroke 

Livonia — Ontario County Line . . 

Livonia — ^Lakeville 

Avon — ^Lima 

Sea Breeze — Nine Mile Point. . . 

Bliss — Smith's Corners 

Wales Center — Wales 

Scottsvilie — Mumford 

Ridge — Rochester — Sea Breeze. . 

Medina — Alabama 

Pavilion — Batavia 

Parma Corners — Spencerport — 
North Chili 



Rolling 


- 
5.0 


Flat 


2.6 


Hilly 


5.0 


Hilly 


8.0 


Hilly 


8.0 


Hilly 


8.0 


Hilly 


8.0 


Rolling 


5.5 


Hilly 


8.0 


Rolling 


5.0 


/ 50 % Flat 


1.5 


I 50% Hilly 


5.0 


Rolling 


5.0 


Hilly 


10.0 


Flat 


6.0 



24 

24 

32 

32 

32 

32 

26 

26 

28 

32 

32 

44 
28-32 
22-30 

32 



2500 
2800 
3600 
5500 
4500 
3300 
6600 
3400 
5700 
3400 

3350 

2800 
2950 

2320 



122 LOCATION, GBADIXG AXD DRAINAGE OF HIGHWAYS 

Taelz 14 [Continued). — Compiued FEOii the E.zcoeX'5 'It z^z. Xz^ Yoek 
State Highway Coioossiox 

Plans for 1908 and 1909 (Selected Roads 



2sa^e of road 



couiiLr> 


iriiprovec. 

grade, 

pec cent. 


:V:-^^^z. 


r-xc- in 
en. Ti 


Rnllmg 


6.0 


30 


1920 


HiUv 


7.0 


30 


3100 


TTilly 


7.0 


32 


■22.50 


\ Flat 


2.5 


28 


2200 


HTllv 


8.0 


28 


2000 


Flat 


5.0 


28-32 


2100 


Hilly 


5.3 


32 


2200 


Hilly 


6.0 


32 


3460 


Flat 


6-0 


22-28 


1960 


HillT 


6.0 


32 


3000 


HUlv 


5.0 


24 


3600 


ffiUv 


8.0 


28 


2550 


Rolling 


4.5 


32 


3000 


Hilly 


7.2 


20-28 


5C00 


KolTing 


6.2 


28 


2000 


; 60 % Flat 
\40% Rolling 


5.01^ 
6.0/ 


26-32 


3100 


Hillv 


9.0 


22-32 


^200 


Hillv 


7.5 


32 


5300 


Rolling 


5.0 


28 


2800 


Flat 


4.6 


24-30 


2240 


Flat 


2.2 


26-30 


2400 


Flat 


4 4 


22 


2174 



Hamburg — ^wcingville Sect. I. . 
Hamburg — Spiingville Sect. XL 

CdUins — Mortons Comers 

Clarence Center 

Oreimd PaA— Griffin's Mills.. 

Coonty Line : 

€ieiieseo — ^Avon 

Genesee — Mt. Morris 

Aldmi — Town Line 

^Pltt^ord — Mendon 

Ktt^ord — Despatch 

Clover Street Section I 

Clover Street Section U 

Rich's Dugway 

Left Fork — German Cliurcti. . . 

Goodrich. Road 

Hamburg — ^North Collins 

Lantern^ — Gowanda 

Chili 

]%o(^ Avenue. . . 

Lydl Avenue 

Barnard'^? Cro^sin^ 



GRADES AND ALIGNMENT 



123 



Table 14 (Continued). — Compiled from the Records of the New York 

State Highway Commission 
Plans for 1910 



Name of road 



Character 

of 

country 



Maximum 
improved 

grade, 
per cent. 



Width of 

section 

between 

ditches, 

ft. 



Exc. in 
cu. yd. 
per mi. 



Lake Part 2 & Sweden 4tli 

Sect [ 

Warsaw — Pavilion i 

East Henrietta — Rochester. . . . i 

Glean — Hinsdale | 

Leroy — Caledonia (1.5 miles), .j 

Shawnee — Cambria 

Roberts Road 



Sanborn — Pekin . 



Oak Orchard, Part 2 

Levant — Poland Center 

Dansville — Mt. Morris, II 

Castile Center — Perry Center. . 
Lake Shore — Lackawanna City 

Eighteen Mile Creek 

Albion Street — Holley 

Pembroke — East Pembroke. . . 



Flat 

Flat 

Rolling 

Flat 

Rolling 

/ 60 % Flat 

\ 40 % Hilly 

Rolling 

Flat 

Rolling 

Hilly 

Hilly 

Flat 

Flat 
- Hilly 
Rolling 
Rolling 



3.8 
5.0 

3.8 



1 
One hill >► 

5.0 J 

4.4 

5.0 

4.1 

3.6 

0.7 

7.0 

3.7 

5.0 



32 

28-32 

32 

28-32 
32-40 

28-32 

32 

32 

30-32 
28-32 

24 

30 
28-32 
28-32 

32 

32 



2560 
3900 
2300 
4000 
1950 

3150 

3230 

2800 

2300 
4000 
6200 
2820 
2120 
6100 
3440 
3800 



124 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Table 14 (Continued). — Compiled from the Records of the New York 
State Highway Commissiox 

Plans from 189S to 1907. (Selected Roads.) 



Name of road 



I -.T • Width of 

Maximum -ection 

Character improved ^'etween 

of country grade ^^ 

per cent. | A ' 



Exc. in 
cu. yd. 
per mi. 



East Avenue Rolling 

Pittsford , Rolling 

Fairport ' Rolling 

Ridge Road Rolling 

Buffalo Road Flat 

White's Comers Plank Road Flat 

Orchard Park Flat 

Transit, Sections I <i: II Flat 

Hudson Avenue Road Rolhng 

West Henrietta Flat 

Scott s^'ille, Section I Flat 

Scotts^'ille, Section II Rolling 

Monroe Avenue Flat 



5.0 


22 


8160 


5.0 


22 


5840 


5.0 


20-22 


6580 


3.3 


26 


2150 


2.0 


22-25 


1700 


3.5 


22 


4600 


3.9 


20 


4200 


4.6 


22 


2100 


3.1 


22 


7100 


5. 5 


22 


3400 


4.0 


22 


2000 


5.0 


22 


2100 


4.5 


22-24 


1850 



An examination of the 1909 report of the New York State Highway 
Commission shows that the largest excavation per mile on roads built by 
the State from 1898 to 1908 was as follows: 

Delaware Turnpike Road 1 . 04 miles. . . 16,800 cu. yd. per mile 

Delaware Turnpike Road 6.5 miles. . . 6,800 cu. yd. per mile 

North Creek-County Line. ...... .4. 12 miles. . . 10.300 cu. yd. per mile 

Highland Lake-Tompkins Cove..". 5. 88 miles. . . 10,100 cu. j'd. per mUe 

and the least excavation as follows: 

Main Street, Section II 986 cu. yd. per mUe 

Babylon-Bay Shore 735 cu. jd. per mile 



GRADES AND ALIGNMENT 



125 



Table 14. — Compiled from the Reports of the Massachusetts State 
Highway Commission, 1896 



Name of road 



Length in 
miles 



Maximum 
improved 

grade, 
per cent. 



Width of 

section 

between 

ditches, 

ft. 



Exc. in 
cu. yd. 
per mi. 



Andover 

Brewster 

Dalton 

Gloucester 

Granby 

Great Barrington 

Hadley 

Munson 

Norfolk 

North Hampton. 

Pittsfield 

Tisbury 

Westport 

Wrentham 

Walpole 

Duxbury 

Fair haven 

Fitchburg 

Goshen 

Marion 

Mattapoisett. . . . 

Lee 

Leicester 



0.6 

1.0 

1.5 

1.6 

0.63 

1.0 

1.49 

0.93 

1.2 

0.56 

1.0 

1.93 

3.0 

1.62 

1.61 

1.05 

1.45 

0.97 

1.91 

1.48 

1.16 

1.5 

2.0 



4.9 

3.36 

6.0 

5.0 

2.7 

2.6 

4.0 

2.95 

5.3 

1.25 

4.25 

4.40 

1.7 

4.0 

6.0 

3.8 

4.0 

6.0 

5.0 

5.0 

4.25 

5.16 

5.0 



24 
21 
30 
21 
21 
21-24 
21 
21 
21 
26 
21 
21 
24 
21 
21 
21 
21 
21 
21 
21 
21 



6000 

2607 

1920 

3200, 

5300 

2300 

8930 

3000 

335Q 

4300 

4700 

7540 

1500 

3700 

5600 

3800 

1200 

4500 

9700 

1500 

1810 

3500 

3800 



No criticism of wasteful expenditure on maximum grade can be 
made in regard to most of the plans as now designed but in many 
instances the profile feature of intermediate grades is not carefully 
analyzed. 

Intermediate Grades. — Intermediate grades include all rates 
between the maximum and minimum grades for the particular job 
in question. They afford the greatest chance for reasonable 
economy of earthwork of any part of the grading design and 
usually receive the least attention. From the standpoint of 
traffic they have practically no value on Local Service Roads 
and only a slight value on Commercial Roads; their proper use, 
however, controls the convenience and suitability of the road to 
abutting property and controlling conditions. In laying a profile 
grade the controlling points must first be considered; these are 



126 LOCATIOX, GRADIXG AXD DRAIXAGE OF HIGHWAYS 

highwater levels of flood areas, elevations of existing bridges, 
railroad crossings, all points where deep cuts or high fills would 
damage the approaches to valuable property connections with 
other liighways, portions of the road previously improved and in 
villages the elevation that will permit future widening and cm"b- 
ing that will fit the case. 

Current practice handles most of these controlhng featm-es 
well with the exception of gi'ades thi'ough villages which are 
almost without exception too liigh for future widening and ciub 
finish. Designers are cautioned to use city street methods and 
to make the elevation the same as if a full width curbed 
pavement was being designed. 

Effect of Intermediate Grades on Cost. — All of these controll- 
ing points must be satisfied but they usually affect only a small 



5+01 10 II 



, Unduloifing Orade^ Proper Use? Serves Excavation ormJ is, 
/ crtffiG SamG Time an Easy Riding Prof He. 
■ AddifioTTcil Rise and Fall on Light Grade Unimportant 




Sfraight Orade^ unnecessary^ y^r^cj'-'^cf Exccvc^t/on 



\Z 



10 



■ Hump of this Kind must be 
f. Dis>regarded 



b^raiqht Orade Proper Uss 



10 V. 11 Tb 24 IS +60Z&+S5 Zl 28 29 3D 
Illuslraiing Proper Use of 
Straight and Undulating Grades 

Fig. 33. 

percentage of the length of an}- improvement and on the gi-eater 
portion of the road the most economical elevation and any 
intermediate rate of gi^ade can be used. A gi-ade so established 
that the cut in every cross-section would just make the fill at that 
poirit would result in the least possible excavation and the 
cheapest kind of gi'ading methods. This condition can never 
be reahzed but the nearer it is approximated the nearer we get 
to the most economical grading design. Where intermediate 
grades are apphcable there is no restriction on any combination 
of rates as they have no eft>ct on traffic loads and very little effect 
on motor operation cost and by an intelligent selection the ideal 
solution can be closely approximated. The cheapest and most 
satisfactory profile can be obtained by the use of the '' rolling 
grade;" by this is meant a profile made up of a combination of 



GRADES AND ALIGNMENT 



127 



^^^ 






^■ 






86*26 



Ot/O^J 



> 






a. 



VA 5 ^- O 



CQ 



L ^ 



kj 



^ 






'.^J<-' 



M 
^ 



Co 



^ 



I 



•iO' 







/■^irS 



128 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

simple, compound or reverse vertical curves, connected by tangent 
grades only when the tangent grade is the most economical or is 
necessary to prevent a series of short humps and hollows. Long 
straight grades are not required, a mistake easily made by engi- 
neers trained in railroad work. Short grades are not objectionable 
and reverse vertical curves ride easily if well built. The rolhng 
grade is also more pleasing in appearance than a straight profile 
if not carried to extremes. The detail methods of laying such a 
grade are described in the third book of this series. It appears 
that there is too much tendency to cut the top of each knoll and 
fill each hollow for very little practical advantage results from 
reducing a natural 4 per cent, grade to a 3.5 per cent, or a 3.5 
per cent, natural grade to a 3 per cent, if the ruling grade is 5 
per cent, and the rise remains fixed. 

We can not overestimate the importance of avoiding this tend- 
ency as the plans of about 2000 miles of road constructed in the 
last ten years which the writer has looked over in this connection 
show a needless expenditure of at least a milKon dollars for grading 
which had no practical value whatever. This element of costly 
design in current practice is probably due to the fact that the 
savings are not spectacular at any one place but if the principle 
is consistently used the total result is spectacular. 

It is also undoubtedly true that the previous railroad training 
of many road engineers has had a detrimental effect on intermedi- 
ate profile design. From the standpoint of highway design rail- 
road practice overemphasizes the elimination of minor rise and 
fall on hght grades. The author has personally apphed the 
''rolling grade'' principle on construction work for the last ten 
years and found that the saving averaged about $500 per mile 
(using the 1920 scale of prices these savings would have averaged 
$1000 per mile). A systematic grade line design will also often 
change the method of grading as well as reduce the yardage. 
To illustrate we will cite the Heber Fruitland Road in Utah. 
The original design used long straight railroad grades which 
required wagon haul; the redesign used a rolling grade which not 
only reduced the amount of excavation by about 30 per cent, 
but also practically eliminated wagon haul for most of the work 
and made it possible to handle the dirt with slip scrapers and road 
machine blade scrapers. This reduced the cost per cubic yard 
about 25 per cent. The quantity reductions plus the unit cost 
reductions amounted to approximately 50 per cent. 



GRADES AND ALIGNMENT 129 

In order to strengthen the force of the argument for ^'rolhng 
grades" the following statement by Mr. G. R. Harr, Office 
Engineer of the Indiana Highway Commission is inserted. The 
work to which he refers was done under the direction of Mr. 
H. K. Bishop, Chief Engineer. 

''When we started here last May a year ago we had some plans 
previously prepared that had long straight tangent railroad grades. 
We revised these plans using rolling grades having long and short 
vertical curves. In so doing we reduced the excavation very materially. 

''From what I remember of the projects and the work on the same we 
saved from about 500 yd. to the mile up to 4000 yd. to the mile. On 
one project the total excavation was cut practically in half." 

The Effect of Arbitrary Profile Limitations on Cost. — A 
common grade line limitation calls for tangent grades drawn to 
intersection with simple vertical curves easing off the apex and 
insists on 100 ft. of tangent grade between the ends of these 
vertical curves. This sounds scientific but has no practical 
value and is cited to illustrate the danger of ill considered limita- 
tions. A specification of this kind often increases the grading by 
from 500 to 1000 cu. yd. per mile an example of which is given 
below. 

PiTTSFORD-N. Henrietta Road in New York State 
Length 2.67 miles 
Original Design Revised Design 

Maximum grade 5 per cent. Maximum grade 5 per cent. 

Profile. — Straight grades with 100 Profile. — Rolling grade. 

ft. of tangent between vertical 

curves. 

Original amount excavation 11,450 Revised amount 9300 cu. yd. 

cu. yd. 

(A saving of 800 yd. per mile) 

In conclusion we may say that the matter of ' intermediate 
grades needs more care than it often receives. 

MINIMUM GRADES 

Hard Surfaced Pavements. — Many road books claim that 
level grades should not be used because of the liability of water 
standing in ruts and that a certain minimum grade should be 
adopted that will insure their longitudinal drainage. Baker 
states in his ''Roads and Pavements" that for macadam roads 
EngHsh engineers use a minimum grade of 1.5 per cent., French 

9 



130 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

engineers 0.8 per cent, and that American practice favors 0.5 
per cent. Let us see what this means. 

For a 1.5 per cent, grade the fall would be j-i in. per ft. 
For a 0.8 per cent, grade the fall would be Ko in. per ft. 
For a 0.5 per cent, grade the fall would be 3^6 in. per ft. 

The flattest crown that is ordinarily used even on bituminous 
macadam is % in. per ft. or twice as much as the greatest longi- 
tudinal fall in the above hst. For long ruts the longitudinal 
grade is of course effective but the patrol system of maintenance 
is supposed to prevent their formation and for short small de- 
pressions the crown slope must furnish the drainage. There 
seems to be no reason why level grades should not be used on 
hard surfaced roads; on such stretches the crown can be increased 
sHghtly to insure transverse drainage and the ditches given a 
minimum longitudinal fall of 0.2 to 0.5 ft. per 100 ft. depending 
on the soil to insure the longitudinal drainage of the surface 
water. 

Earth Roads. — -On earth or gravel roads attention should be 
given to minimum grades as for these types they have some value 
but not enough to warrant much expenditure. 

It is advisable to use a 0.4 per cent, to 0.5 per cent, grade 
where much snow or rain occurs but in the arid regions no mini- 
mum restriction should be specified. 

Adverse Grades. — Adverse grades are defined as grades con- 
tary to the general rise and fall of the road between terminals 
or controlHng points. It is important to avoid them on mountain 
road locations where the prime object is to gain elevation or on 
main Commercial Roads where the factor of rise and fall has 
considerable value. They are not a serious drawback for the 
usual road and can not be avoided in ordinary rolhng topography. 
This is so self-evident that it hardly seems necessary to state it. 
There is no serious objection to short adverse grades even on a 
long chmb if by their use the ahgnment can be bettered and 
excavation saved in crossing a small guUy. There is no objection 
to adverse grades of 2 per cent, or less on any road. The main 
objection is to long adverse grades introducing considerable 
additional rise and fall which could be avoided by a better 
engineering location. This point is generally considered in the 
selection of the general route and is covered by the comparison 
of routes in the preliminary investigation. 



GRADES AND ALIGNMENT 



131 



Vertical Curves. — Vertical curves between tangent rates of 
grade add to the safety, convenience and appearance of the 
highway. Vertical curves as a rule are picked out to fit the 
natural profile and in easy rolUng topography this method of 
selection need not as a rule be modified for any other considera- 
tion. However, there are cases where the length of the vertical 
curve at the summit of a hill controls the length of sight ahead 
and under these conditions certain minimum lengths are stipu- 
lated. A reasonable basis for decision in these cases appears to 
be founded on a clear sight ahead at all times of 350 ft. for Main 
Commercial Special Service roads and 250 ft. for Local Service 
roads except in mountainous regions where the sight distance 
requirement can not be reasonably obtained. On this basis the 
following table is compiled assuming that the line of sight is 5.5 
ft. above the ground at the two ends and tangent to the vertical 
curve. 

Table 15. — Based on a Line of Sight 5 ft. 6 in. Above the Ground 

AT Both Ends 



Algebraic difference in 
of grade per cent. 


rates 


^linimum length of vertical 

curve in feet for a sight 

distance of 250 feet 


Minimum length of vertical 
curve in feet for a sight 
distance of 350 feet, feet 


6 




' 








8 










150 


10 




50 






250 . 


12 




135 






330 


14 




190 






400 


16 




225 






450 



As a matter of fact merely on account of appearance and con- 
venience in motor operation to prevent disagreeable checking 
in speed at the foot of hills the author never uses a vertical 
curve less than 100 ft. long between grades having an algebraic 
difference in rate of 5 per cent, or less. Vertical carves are 
generally used between all grades having an algebraic difference 
of over 3^-2 of one per cent. 

Minimum length of vertical curves from the standpoints of 
convenience, appearance and sight distance can be assumed 
roughly as follows. There is no limitation on maximum length 
except that the curve should fit the profile without excessive 



132 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

grading. Vertical curves should be made as easy as possible 
without running up the cost needlessly. 

Table 16. — Recommended Minimum Lengths of Vertical Curves 
Between Tangent Grades 



Algebraic difference in rates 

of tangent grades, 

per cent. 


Minimum length of vertical 

curves on local service roads, 

feet 


Minimum length of vertical 
curves on special service 
commercial roads, feet 


5 or less 


100 




100- 150 


8 


150 




200 


10 


200 




300 


12 


250 




* 400 


14 


270 




450 


16 


300 







Summary of Grades. — ^The discussion of economic grading 
design may be summarized as follows : 

The road value of reasonable maximum grades and small 
amounts of rise and fall on steep grades can not be overestimated. 
Any expenditure on these features is justified so long as it is 
consistent with the theory of cheap operation. The use of 
properly proportioned short maximum grades in connection 
with long ruhng grades is a source of justifiable economy and 
works no hardship except for long trailer trains. The use of 
the highest reasonable maximum to shorten distance for a fixed 
rise results in considerable construction saving in many cases 
and is justified on the score of reducing motor operation costs. 
Distance should never be increased for a fixed rise to reduce grades 
helow a reasonable maximum. 

Minimum center fine grades have no road value on hard 
surfaced roads and only a shght value on earth roads. Minimum 
ditch grades are important. 

The traffic value of intermediate grades is negligible on local 
service roads and only of minor importance on Special Service 
roads. Intermediate grade fine design has a large effect on 
grading cost and is entitled to very careful consideration. The 
most common faults of the ordinary treatment of these grades 
are the needless reduction of hght natural grades and the use 
of long straight railroad rates of grade. There is no practical ad- 
vantage whatever from the use of long uniform light rates of grade 



GRADES AND ALIGNMENT 133 

where the total rise and fall is not changed and very little real value 
is accomplished hy the reduction of minor rise and fall occurring 
on light natural grades. 

ALIGNMENT 

Alignment affects the safety, speed, ease and hauKng power 
of traffic and the cost of Road Construction. Highway location 
is controlled at many places by the effect of curvature on maxi- 
mum grade and the effect of alignment on construction cost. 
Sharp ahgnment modifies the allowable rate of grade, the width 
of pavement, width and shape of section and increases the need 
for substantial safety devices such as retaining wall or concrete 
or steel cable guard rail. At this point in the discussion it is 
only necessary to consider the factors in connection with align- 
ment which would naturally control the field survey location 
namely; the effect of alignment on grade, cost of construction 
and safe sight distance for traffic. The effect of alignment on 
banking and widening pavements on curves and on the design 
of guard rail, etc. will be taken up in Chapter V and Volume II. 

In well settled communities alignment is practically con- 
trolled by the existing road right of ways except where short 
relocations will materially reduce distance, needless rise, extreme 
grade or danger to traffic. In sparsely settled communities 
alignment is not handicapped by right of way difficulties. 
As a general proposition dangerous or crooked alignment should 
not he introduced to reduce grades below the maximum. If it is 
necessary in order to get the maximum grade or to keep the 
construction cost within reason well and good. By this is 
meant that a straight road on a 5 or 7 per cent, grade is generally 
more satisfactory than the same road on a 3 or 5 per cent, grade 
with a dangerous turn. If the lower grade can be obtained 
without dangerous alignment and without increasing distance, 
all well and good. However, a reasonable maximum grade should 
not be sacrificed on a side hill location for better ahgnment as 
future improvements, grading, etc. can reduce ahgnment danger 
much more easily than it can reduce grade by an entire relocation 
and the danger at a few sharp bends on a long climb having 
normally safe alignment can be reduced by flattening the grade 
at the danger point. That is the necessity of one or two sharp 
switchback turns to get a long reasonable maximum rate would 
not warrant an increase in grade above the reasonable maximum 



134 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

in order to eliminate these tinns. Short maximums in connec- 
tion with long lower maximums are warranted to improve 
ahgnment. 

Dangerous Alignment. — Sharp curves are not particularly 
dangerous for slow horse trajfic but they are extremely danger- 
ous for high speed motor traffic particularly on through roads used 
by drivers not famihar with the locahty. It is of course im- 
possible to protect traffic from the carelessness of speed maniacs 
but the danger of collisions can be materially reduced by ahgn- 
ment which permits the driver to see ahead a reasonable cUstance 
at all times. Cars driven at high speed are hable to leave the 
road on almost any curve as the author's observation has been 
that about as many cars go off moderately easy curves up to 
500 racHus as they do en very sharp curves on account of the 
tendency to take the easier curves at excessively riigh speed. 
However, the danger of collision is less as it gives the other man 
a chance to protect himself. We are not particularly grieved 
if a fool does commit suicide. A toaring speed of 20 to 30 miles 
per hour is reasonable for main road travel in ordinary roUing 
topography. Tests on the braking power of automobiles show 
that a passenger car travelling 20 miles per hour can be stopped 
in 40 ft., and one going 40 miles per hour in 140 ft. by the use 
the emergency brake. As a matter of fact, brakes are not always 
efficient, a driver requires a httle time to reahze that danger 
exists after first seeing the approaching car so that the deter- 
mination of safe sight chstance is largely a matter of judgment. 

Sight Distance. — The author has written to a large number of 
Automobile Clubs over the countr\" and in the main they agree on 
250 to 300 ft. as the minimiun safe sight chstance ahead at aU 
times. The shorter distance is used on local service roads 
where most of the drivers are famihar with the road and the 
longer distance for main routes carrying foreign traffic not 
famihar with the existing ahgnment. This corresponds with the 
practice of various highway departments. Roads built with 
this limitation seem satisfactory^ to traffic. A sight distance of 
this kind does not necessarily depend on ahgnment unless the 
curve is in cut. Ahgnment is not affected by sight distance 
unless the curve is in cut or along a side hiU where the cut slope 
is on the inside of the curv^e or where buildings or trees occur 
along the right of way hne. The smaUest radius of curvature 
that is permissible to give a certain sight distance depends on 



GRADES AND ALIGNMENT 



135 



the width of the road section in cut and can be easily worked out 
diagrammatically for any special case. To give an idea of the 
various minimum alignment radii required for the different 
sight distances for curves in cut the following table is inserted. 



150'Sight 
A B 



158 



286 



ZOO'Sight 

Distance 

A B 



21? 



ZBOSight 

Di stance 

A I B 



300 Sight 
Distance 
A I B 



■350 Sight 
Distance 
A B 



VdluesgivGn below are the radii in feet 
505 I 420 I 786 I GOO I 1130 1 815 



1536 



400 Sight 
Distance 
A B 



1062 



2005 




■l9'(fipprox.)- 



Line of Sight on 
Sfraigh-h Grade S> 




-10-0--- 



Contracted Section in Deep Cuts. 
This is the Section on which this Table is Based 



Table 17. 



This table is compiled for the minimum width section used in 
New York State in 1919. Similar tables can be prepared for the 
standard sections in use in any particular locaHty. Column A 
in each case apphes where the carve is on a straight grade and the 
line of sight is 5 ft. 6 in. above the crown grade of the road. 
Column B in each case applies to where the curve is at a change 
of grade and the line of sight is just above the ground at the 
ditch line. 

The radius for a specified sight distance can be figured by 

M C^ 
the formulae R = -w + ^Tf where 

R = The road (t. radius in feet. 

M = The distance in feet off the (^ of the road where the line of 
sight comes tangent to the cut slope or any other obstruction. 
C = Required length of sight distance in feet. 

The sight distance for any specified alignment radius and 
standard section can be increased by ^'Daylighting" the curve as 
shown in Fig. 35 (page 136). 

This method has the distinct advantage of cheapening the 
grading cost and it also gives the driver a chance to see ahead 
even if he hugs the inside of the curve. 



136 LOCATIOX, GRADING AND DRAINAGE OF HIGHWAYS 

Figure 36 shows a proposed improvement of this nature on 

State Route 30 Xew York State. 

Current Practice Minimum Curvature. — Sharp em-ves on 
steep grades or at the foot of such grades are not safe. Good 




.Bench cuf cut of Slope 



1 



> ; Ba nked One WcK/CnAw? 




Fie. 35. — " DayUghting" a curve. 

practice calls for a minimum radius of SOJ to -iOO ft. for these 
eases in ordinary topography. Right angle turns even on level 
stretches are an abomination of the Lord. A minimiun radius of 
200 ft. for such cases increases the convenience of the road and 
is greatly appreciated by the road users. 









j Proposed Bene 


h Cut. 




»» • . 




<■ 


»«r 









Fig. 36. — ^^;:.izr:.z.z i, lur-r i_iin interciry siare rou:e 1.0. 30 .Xe"^ York 

State). 
7. ; u:^5 01 curvature road center line 1>" i' 
Piriri.: sight distance 240 ft. 
Proi>o=ed sight distance 340 ft. 

France and Austria have used minimum radii of 100 to 165 ft. 
on main roads and as low as 50 ft. radii on District roads but 
these hmits are hardlv suitable for fast traffic. The use of 



GRADES AND ALIGNMENT 



137 




Fig. 37. — 200 ft. radius curve in background on 3 per cent, grade. Serves 
traffic well. This road is a State Route in New York State carrying approxi- 
mately 1500 vehicles per day in summer. 




Fig. 37A. — Dangerous bridge approach alignment radius of curvature 76 ft. 
Alignment of this kind is very poor practice. 



138 LOCATIOX, GRADIXG AXD DRAINAGE OF HIGHWAYS 

tractor trailer trains, 4 or 6 horse teams or the haiihng of long 
timber sometimes hmits the radius of a curve. 

Rear Wheel Encroachment. — Under these conditions it is 
desirable to widen the section on the inside of the cmve to pro- 
vide clearance for the last wagon or the back wheels of a long ria; 
as they work in towards the bank. To approximate roughly the 
distance that the last wheel works inside of the front guide wheel 
track we will assume that the rig has a stiff connection between 
the front and rear axle. This will give a result on the safe side 
as for a loosely coupled train or a special swinging rear axle much 
sharper corners can be turned. 



. Fa fh o f I n side fron f r/h<?el or C.L.of r^cad 



--'^afh of inside back whe<?l 




^/ Formal! oratinary ccs<?^ W can b<? 
<^y ■appraximcffs'd b^ fre fo!!o w)nq formufar- 



Fig. 3S. 



/ = Length of rig between front and back axle. 
R = Radius of circle traveUed by inside front guide wheel. 
TT' = Encroachment of back wheel in making curve. 
(See table 18, page 140). 

Mountain Road Alignment. — In mountain road location it is 

generally impossible to pro^'ide a safe sight distance as it would be 
prohibitive in cost. For such conditions considerable must 
be left to the care of the driver and the limitations of alignment 
are based more on the cost of construction than on the safety of 
traffic. Where long timbers are hauled over the road the fore- 
going table indicates the extra width or racHus required. 

Effect of Alignment on Grade. — -On sharp cmwes it is desirable 
for the driver to have hrst-class control on the score of safety. 
An extremely sharp cm've with a large central angle also reduces 
the hauhng capacity of a six horse team by from 20 to 40 per 



GRADES AND ALIGNMENT 



139 




Fig. 39. — Example of first class side hill alignment. Also note liberal width 
of clearing to increase sight distance and to permit the sun to reach the road 
and melt snow. 




Fig. 40. — Example of ordinary side hill alignment. 



140 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

TABI.E 18. — Table of Approximate Encroachment of Rear Wheel 

Inside of Path of Front Wheel for Different Lengths of Rig 

AND Different Radii of Road Center Line Assuming that 

the Central Angle of the Curi'te is Large Enough to 

Produce the Full Encroachment. This Generally 

Occurs when the Cur^^b is Two or Three Times 

AS Long as the Length of the Rig 



Length, of rig between front and rear axle in feet 



Approx. radius of 

road center line in 

feet 



10 



20 



30 



40 



50 



The values given below are the approximate distances in feet that 
the rear wheel runs inside of the front wheels. 



40 


1.3 


5.4 




• 




50 


1.0 


4.2 


10.0 






60 


0.8 


3.4 


8.0 


15.3 




70 


0.7 


2.9 


6.8 


12.6 


21.0 


80 


0.7 


2.5 


5.8 


10.7 


17.5 


100 


0.5 


2.0 


4.6 


8.4 


13.4 


120 


0.4 


1.7 


3.8 


6.9 


10.9 


150 


0.3 


1.3 


3.0 


5.4 


8.6 


200 


0.2 


1.0 


2.3 


4.0 


6.4 


300 


0.2 


0.7 


1.5 


2.7 


4.2 


400 


0.1 


0.5 


1.1 


2.0 


3.1 



Note. — According to Droune the first pair of horses will occupy about 
13 ft. ahead of the wagon and each additional pair 10 ft. more each. Wagons 
range in length from about 10 ft. for the bottom damp type to 50 ft. for 
trucks hauling timbers. The ordinary commercial 5-ton truck has a wheel 
base of 14 to 17 ft. Recent regulations limJt the length from 20 to 30 ft. 
over all, and the total length of trailer trains to 90 feet. 



cent. Considering both safety and team hauling it is therefore 
desirable to reduce ruhng grades on sharp curves. These con- 
siderations have no practical value on mountain roads for curves 
having radii greater than 100 ft., but on sharper curves good 
practice recognizes this principle. Ordinary design uses radii 
of from 40 to 80 ft. on difficult switchback turns. For a 40 ft. 
radius the grade should not exceed 3 per cent, and for an 80 ft. 
radius 4 per cent, is a reasonable maximum. For high class roads 
in well settled districts at points where the sight distance is less 
than 350 ft. for commercial roads or 250 ft. for secondary state 
routes or local service roads the grade should not exceed 3 
per cent. 



GRADES AND ALIGNMENT 



141 



Effect of Alignment on Motor Operating Costs. — Dangerous 
sharp alignment increases motor operating costs. It decreases 
normal speed and results in the needless use of second or low gear 
climbing and excessive braking on down grades. This action 
only occurs, however, on a very small percentage of the distance 
on a well designed road, viz.; at the danger points. That is if 
the alignment is safe for traffic it does not affect the operating 
cost. If it is dangerous for traffic it does affect the operating 
cost. As real danger is a more vital matter in the design than 
cost of operation, alignment design is controlled by the factor of 
safety and not by considerations of operating cost. That, is; 
danger will be eliminated if it is possible to do so and no con- 
sideration of cheaper operation would improve the alignment 
if the consideration of danger had not been sufficient to warrant it. 

While there is no good data on the effect of alignment on 
operating cost, we have enough general data to state with 
reasonable assurance that if the radii of curvature are not 
sharper than from 250 to 300 ft. on the level or less than 400 
to 600 ft. on grades and the sight distance is not less than 250 
ft., that reasonable speeds need not be reduced on account of 
alignment and that motor operating costs are not materially 
affected. For sharper curvature and shorter sight distance the 
cost of operation is probably increased. How much we do not 
know, but purely as a matter of academic interest the author 
has modified the factors used in compiling table 12 for usual 
alignment, to conform with certain observed speeds on danger- 
ous alignment. The following graph shows the result. 

Curve ''A" represents safe alignment. Curve *'B" repre- 
sents dangerous alignment. 



P <:g O cc Ooo 



50 



40 




10 





















^ 










c^ 


II 


*^ 


■^ 




^ 










£5^ 


r^' 


<" 










— 




"^ 



































bO 



40 





20 <§ 



10 



2 



3 4 5 6 T 

Rate of Grade, Per Cent 



10 



Graph illustrating approximate effect of dangerous alignment on motor 
operation costs. (Time factor included). Curve "A" safe alignment (based 
on Table 12 A, colume I, page 100). Curve "B" dangerous alignment. 
(Operation factors modified for sharp alignment). 



142 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

The general condusioii to he draivn is that motor operation is 
cheaper an good alignment and that if alignment can he m<ide safe 
hy steepening the rate of grade that a slight increase in rate will 
not add to motor operation costs over that required for the lower 
rate and poor alignment. 

In conclusion we may say both from the standpoints of 
safety and operating costs, that it is desirable to design special 
service commercial roads for a sight distance of about 350 ft. 
and local service or secondary state routes for about 250 ft. 
Considerable expenditure is justified to obtain this requirement 
but large additional cost in order to further increase the sight 
distance is wasteful and poor engineering, particularly on roads 
of secondare' importance. This caution is not a needless one 
as the author has recentty heard designers excuse excessive 
profile and section grading on the score that it increased the 
sight distance beyond the 350 ft. limit. This limit is not nec- 
essarily proper or liberal enough for all conditions, but it seems 
good sense to arrive at some limit suitable for the road in question 
and then eliminate additional expenditure for an additional 
sight distance which maj' be fine to have if you can afford it, 
but which is really not necessary. The tendency of almost all 
departments working with large appropriations is to gradually 
increase the fancy extras which may not amount to much for one 
case but grow in number like a snow ball until you wonder why 
the cost of roads are going up and the mileage for yom- appro- 
priations coming down. 

Effect of Alignment on Construction Cost. — For high class road 
improvements in ordinary topography alignment does not" have 
much effect on cost of construction. There is no particular 
object in long tangents and where an old road is being paved it 
is just as well to shift the center line slightly to keep on the old 
travelled way and take advantage of the old grading and any 
hard metalling that may have been placed in the past. Slight 
variations from the center of the right of way often save some 
grading expense and improve the character of the subgrade 
for the pavement. 

In mountain road location, ahgnment is given careful con- 
sideration as it has a marked effect on cost. The radii are made 
as large as possible to fit the mountain side without excessive 
gracUng. On steep slopes the grade contour must be followed 
closely (see Figs. 41 and 42) . There is no hesitation in using radii 



GRADES AND ALIGNMENT 



143 




Fig. 41. — Alignment following grade contour closely (New Mexico). 




Fig. 42. — Example of crooked alignment on steep mountain slope. New road 
above and to the left. Old road below and to the right. 



144 LOCATION, GRADIXG AND DRAINAGE OF HIGHWAYS 

as sharp as 80 ft. at the head of gullies where the driver can see 
across the curve or a radius of 100 ft. on the outside cm-ves around 
points where the sight cUstance depends on the radius. Even 
these h'mi'ts are impracticable in very rough country where 
radii of 40 ft. are considered reasonable. All outside curves 
having a sight distance of less than 250 ft. should be posted with 
danger signs. 

The arbitrary hmitation of minimiun racUus has a large effect 
on cost. The following example will illustrate this point. These 
revisions were made by C. H. Chilvers on the Rabbitt Ears 
Pass Road in Colorado to show the effect of ahgnment on 
excavation. 

The office method of plotting a good cheap ahgnment are 
described in detail in the third voliune of this series. 



R-^BBiT Eabs Road, 


State of Colorado, 


Side Hill Sectiox 


Original design 


First revision 


Second re%"ision 



Length, 8.79 miles. 
Width of roadway, 16 ft. 
Maximum grade, 8 per 

cent. 
Grades flattened on 

switchback turns. 
Minimum radius 100 ft. 
Firs t-class alignment 

throughout. 



Total amount of exca- 
vation, 91,000 eu. yd. 

First-class design but 
needlessly expensive. 



Length, 8.81 miles. 

Width, 16 ft. 

Maximum grade, S per 
cent. 

Xo grade compensation 
on cur^'es. 

^linimum radius, 100 ft. 

First-class alignment , 
but more cur^'ing elimi- 
nating many expensive 
tangents. 

Amount of excavation, 
65,000 cu. yd. 

First-class design shows ! 
effect of careful, intelli- 
gent alignment engi- 
neering. 



Length, 8.94 miles. 
Width, 16 ft. 
Maximum grade, S.o per 

cent. 
No compensation on 

curves. 
Minimum radius, 40 ft. 
Poor, crooked alignment 

carried to extremes. 



Amount of excavation, 
38,000 cu. yd. 

Illustrates extreme effect 
of ahgnment on cost. 

From an engineering 
point of -view there 
was no justification for 
this design for the 
topography in question. 



Xote. — On one switchback turn on this road a 100-ft. radius required 
5000 cu. yd excavation and a 40-ft. radius 500 cu. yd. or one-tenth as much. 
Short radii are justified in isolated cases but their continuous use to save 
small amounts is poor practice. 



GRADES AND ALIGNMENT 



145 




Fig. 43. — First class switchback design. Note flattening of grades on sharp 

turns. 




Fig. 44.— Poor switchback design, alignment too sharp. Grades not reduced 

on turns. 



10 



146 LOCATIOX. GEADIXC- AXD DRAIXAGE OF HIGHWAYS 




Pig. 45. — Excellen": switchback layout on spur location. Note grade flattened 

on curve. 




Fig. 46. — Retaining wall switchback construction. 



GRADES AND ALIGNMENT 



147 



Effect of Railroad Grade Crossings on Alignment and Grade. — 

Railroad grade crossings are sources of continual danger; they 
should be eliminated on all main routes. The discussion of sub- 
way and overhead eliminations is given in Volume III. If a grade 
crossing is necessary the best practice calls for a tangent crossing 
at least 400 ft. long 200 ft. on each side of the track. It is not 
advisable for the tangent to make an angle of less than 60° with 
the center line of the track. The approach grades should not 
exceed 5 per cent, and a level grade at least 50 ft. long should 
be provided on both sides of the track to permit the better control 
of the vehicle as it approaches the crossing. 

Anyone owning an automobile is famihar with the dangerous 
element of driving where precautions of this nature are neglected. 




Fig. 47. — Example of flattening grade on switchback turn, 
built of stone posts and wire cable. 



Also note guard rail 



Recommended Alignment Practice. — The following summary 
agrees with general current practice and can often be used with- 
out raising the cost beyond the bounds of reason. A summary 
of this nature is of course of only general value. Each case must 
be worked oat on its own merits. Broad generalizations of 
detail requirements are dangerous if used indiscriminately. 

Main Commercial Roads. (Wetl Settled Districts.) 

Minimum sight distance 300 to 400 ft. 

Minimum radius of curvature at right angle turns on level 

outside of villages where sight distance does not control. . 250 to 400 ft. 

Minimum radius of curvature on steep grades or at the foot 
of such grades depending on the central angle where the 
sight distance is not the controlling factor 400 to 600 ft. 



148 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Ordinary Agricultural Roads. (Local Service.) 

Minimum sight distance 200 to 250 ft. 

Minimum radius of curvature at right angle turns on level 

outside of villages 100 to 200 ft. 

Minimum radius of curvature on steep grades where sight 

distance does not govern 300 to 400 ft 

Mountain Roads. 

No limitation on sight distance. 

Warning signs used where necessary. 

Minimum radius on steep grades 100 ft 

Minimum radius in extremely rough country 40 ft. Grades not to exceed 
3 per cent, for a 40-ft. radius and not to exceed 4 per cent, for an 80-ft. 
radius. Any grade up to 8 per cent, on a 100-ft. radius, although it is 
desirable not to exceed 5 per cent, on a 100-ft. radius curve with a large 
central angle. 

Summary of Principles of Location. — Climatic, drainage and 
soil conditions govern a location in respect to avoiding bad snow 
conditions, flood areas, needless stream crossings, slide or swamp 
formations and excessive rock work. The general requirements 
of line and grade discussed in this chapter are summarized as 
follows : the various principles are repeated conversely under the 
headings of Grade, Alignment, Distance, Rise and Fall and Cut 
and Fill grade reductions. 

First. — Reasonable maximum grades are essential. Recom- 
mended reasonable rates for various kinds of roads are given 
on page 116. The following treatment is allowable to get a 
reasonable maximum. 

{a) Any expenditure necessary, 

(6) Distance may be increased in order to get a reasonable maximum 
grade but should not be increased for a fixed rise to reduce grades below a 
reasonable maximum. 

(c) Poor alignment may be used if necessary to get a reasonable maximum 
grade if funds are low but poor alignment should never be introduced to 
reduce grades below a reasonable maximum. Where poor alignment is 
necessary maximum rates must be reduced at the danger points (see page 
140). 

(d) For a fixed rise and distance, it is generally better to use a short 
length of reasonable maximum and the balance of the distance a low rate 
than to use a uniform moderate rate grade for the entire distance; this is 
not strictly in accord with the principles of cheap motor operation (table 
12B, page 104) but the net practical results are generally better. This 
means that if a road is running up a valley on an easy grade and must leave 
the bottom land and climb on a side hill location to reach a pass that it is 
generally better to make the climb as short in distance as possible as a side 



GRADES AND ALIGNMENT 149 

hill location usually introduces poor alignment and generally increases the 
excavation per mile over a valley location. 

Second. — Alignment should he mode as safe as possible con- 
sidering the funds available. Safety of traffic governs alignment 
practice. Cost of traffic operation has no practical effect. 

(a) Good alignment should never be sacrificed to reduce grades below 
a reasonable maximum. For safe alignment practice (see page 147). 

(6) Good alignment may be sacrificed to get a reasonable maximum 
but this condition necessitates the reduction of grade at the danger points. 
(See page 140.) 

(c) Improved alignment warrants increased distance only when danger is 
eliminated. Increased distance is not warranted merely to make an easy 
curve easier. 

(d) It is better to use a steeper grade (up to a reasonable maximum) 
with good alignment than to use poor alignment and a lower rate. 

(e) Exceptionally good alignment (practically straight) may in some 
cases warrant an increase in the reasonable maximum grade above the 
rates recommended on page 116. This modification would not however 
apply unless it was impossible to locate and grade the lower rate location 
so that the sight distance on it was at least 250 ft. 

(/) An alignment and grading design w^hich results in a sight distance of 
250 to 350 ft. is safe and desirable but large expenditures to still further in- 
crease the sight distance must be used with caution unless the funds are 
practically unlimited. Increase in maximum grade above the recommended 
maximum in order to increase sight distance above 250 to 300 ft. is rarely 
warranted. 

Third. — Short distance is desirable provided considerations 
of safety, rise and fall, or reasonable maximum grades do not modify 
the conclusions. 

(a) Distance may be increased to reduce danger by better alignment 
at bridge approaches, railroad crossings, or to avoid difficult topography. 
Recommended minimum radius of curvature are given on page 147. 

(6) Distance should be increased to get a reasonable maximum for a 
fixed rise but rarely to reduce the grade below a reasonable maximum for a 
fixed rise. 

(c) Distance should never be increased to reduce rise and fall on grades 
of 2 per cent, or less. 

(d) Distance may be increased to reduce rise and fall on grades over 2 
per cent, (use table 12B for comparisons of this kind) but for grades not 
exceeding the maximum it is rarelj^ desirable to increase distance unless a 
noticeable rise and fall can be eliminated by a small additional distance. 
For ordinary easy rolling topography the principle of the straight line location 
is generally sound. 



150 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Fourth. — The elimination of needless rise and fall is desirable 
modified by certain conditions. 

(a) The eliminatioi] of rise on steep grades is desirable. Distance may 
be increased to accomplish this provided the disadvantage of increased 
distance is balanced against the value of less rise (see table 125, page 104). 

(b) The elimination of rise on grades of 2 per cent, or less is of no value 
from a practical standpoint. 

(c) Adverse grades may be used to eliminate dangerous alignment or 
shorten distance provided the shorter distance is of more value than the 
disadA-antage of the extra rise (see table 125). 

Summary of Cut and Fill Grade Reductions. — Grade reduc- 
tions by cut or fill assume that the road location is fixed for some 
reason and that further improvement must be by cut or fill. 
The distance is always fixed. Reasonable maxi7num grades are 
essential. 

[a] For a fixed rise there is no practical advantage in reducing the rate of 
grade below a reasonable maximum. 

(6) Reduction of total rise and fall on steep grades is desirable. 

(c) Reduction of rise and fall on light grades has no practical advantage. 

{d) The use of short adverse grades of 2 per cent, or less on a long climb 
has no practical disadvantage. 

The sources of justifiable economy in cut and fill design 
lie in the use of the short maximum in connection with the long 
ruling grade and the use of a rolling grade profile for all inter- 
mediate rates. 

The application of these principles in conjunction with the 
"spotting method" of profile design generally results in a satis- 
factory road at a moderate grading ccst. The Auolation of these 
principles of location and cut and fill profile design occur Cjuite 
frequently. 

Conclusion of Chapter. — The considerations discussed in this 
chapter govern the engineering field location and in conjunction 
with the variation in road cross section determine the effective- 
ness and economy of tne grading design. The methods of their 
practical application are taken up in the third book of this series 
by means of actual designs worked out in detail and modified by 
systematic criticism. 

Grades and ahgnment are fundamental permanent features of 
highway improvement. There should be no hesitation in spend- 
ing all the money that may be required to get satisfactorv results 
for average traffic but extreme refinements of location may will 
weh be avoided if thev materiallv increase the cost. 



CHAPTER V 

CROSS SECTIONS OF RURAL ROADS, WIDTHS OF PAVE- 
MENT, RIGHT OF WAY AND CLEARING 

The shape and width of road cross sections have considerable 
effect on the safety and convenience of the highway for traffic and 
they also affect the economy of grading design. It is desirable to 
obtain features that are fundamentally required for the satisfac- 
tion of traffic but it is also desirable to avoid arbitrary standard- 
ization which adds materially to the cost without any adequate 
benefit. The problem of sections can be summed up as the 
determination of the minimum widths of grading, pavement, 
etc., the mim'mum depth of surface ditches in cut and variations 
in shape and width that will serve the present traffic requirements. 

At the time a road is improved, right of way should be ac- 
quired of such a width that it will permit the future widening of 
section, pavement, etc. Liberal right of way can be obtained 
more easily during the first stages of road improvements than 
at a later time when the land is worth more and buildings have 
been erected close to the road. That is right of way considers 
the future requirements of the road but grading widths can only 
reasonably consider the requirements of existing traffic. 

Sections. — Sections can be considered from the standpoints of 
Safety, Convenience and Economy. 

Safety requires a grading shape that permits the rig to use any 
part of the road from ditch to ditch without overturning or if 
this is not possible various expedients such as the one way crown, 
banking on curves, guard rail or wall protection will very mate- 
rially help the traffic. Safety requires a liberal sight distance 
which on sharp curves can be obtained by ''Day lighting" the 
section (see Figs. 35 and 36, page 136). 

Convenience requires sufficient width for vehicles to pass at 
any point in ordinary topography and provides special turnouts 
at short intervals on Mountain Roads. It also calls for crown 
and shoulder slopes that permit driving without an uncomfort- 
able side tilt to the rig. 

151 



152 LOCATION, ORADIXG AXD DRAINAGE OF HIGHWAYS 

Economy of grading calls for various combinations of widths, 
ditch depths, back slopes, etc. which most nearly fit the natural 
conditions at all points. That is the section must be flexible. 

It is, perhaps, best to develop the discussion of sections and 
pavement widths first for the high class road in ordinary topo- 
graphy and second for pioneer roads in mountainous conditions. 

High Type Roads (Premises of Design). — The points to be 
considered in the development of a normal section are: 




Fig. 4S. — Banked curve on high class road protected by substantial concrete 

guard rail. 



1. What is a safe driving slope? 

2. What is a comfortable driving slope? 

3. What pitch is required to drain different surfaces? 
These factors determine the shape of the section. 

4. What is the commonly used width and the maximum width 
of the travelled way? 

These factors determine the TN-idth of pavement and shoulder. 

5. What is the minimum allowable depth of surface ditch? 

6. What are stable slopes for cut and fill outside of the limits 
of the travelled section? 



CROSS SECTIONS OF RURAL ROADS 153 

These factors affect the economy. 

The first three questions have been pretty well settled by 
current practice; the last three are not so well defined. We will, 
however, assume the following premises which can be modified 
for special conditions: 

1. Three inches to 1 ft. or 4:1 is the maximum safe driving slope. 

2. One inch to 1 ft, or 12:1 is the maximum agreeable driving slope. 

3. One inch to 1 ft. or 12:1 is the minimum slope at which an earth 
shoulder will shed water without too much maintenance. Three-fourth inch 
to 1 ft. or ^i in. to 1 ft. is a satisfactory crown for a single track Waterbound 
Macadam Road and }-2 in. to 1 ft. is a satisfactory crown for a double track 
Waterbound Macadam pavement. Three-eighth inch or 3^ in. to 1 ft. is a 
satisfactory crown for double track Bituminous Macadam pavements or 
waterbound macadam treated with tar or asphalt flush coats. One-fourth 
inch or % in. to 1 ft. serves very well on rigid pavement types such as brick, 
concrete, sheet asphalt, etc. , Circular arc or parabolic crowns are more 
satisfactory than the straight line section for the pavement proper. 

4. The width of roadbed subjected to hard wear by traffic on the lighter 
traveled roads (single track roads) ranges from 8 to 10 ft. and on double 
track roads from 14 to 17 ft. The maximum width of roadwaj^ subjected 
to some wear by traffic turning out to pass ranges from 18 to 22 ft. 

5. The minimum ditch depth below crov/n grade depends on keeping 
the longitudinal surface water outside of the travelled way and is rarely 
less than 10 in.; it depends largely on the amount of surface water that must 
be cared for. 

6. The stable cut and fill slopes depend on the climate and the material 
and range from 3'^:1 to 4:1. 

Before proceeding further, it will be just as well to discuss a 
little more fully, items 4, 5 and 6. 

Widths of Travelled Way (Item 4). — The width of roadway 
carrying the greater portion of the travel and the maximum 
widths when rigs turn out to pass are not well established. They 
are affected by the volume and speed of traffic, the pavement 
crown, and the width of vehicles. 

Effect of Crown. — Crown has a marked effect on width of heavy 
travel. A crown such as % in. to 1 ft. or 1 in. to 1 ft. tends to 
concentrate the traffic in the center and is a detriment on a heavy 
traffic road. With crowns of J^ in. to 1 ft. or less there is no 
tendency to concentrate. For single track macadam or gravel 
roads where the traffic tends to stay in the center of its own accord 
on account of infrequent passing of rigs a fairly heavy crown is 
desirable as it is easier to maintain. On double track roads a 
crown of }^ in. to 1 ft. or less should be used both on account of 



154 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 




13 

c3 
O 
li 

W) 

a 

© 

'ft 

13 
Pi 
o3 



I 

oi 

d 

M 



CROSS SECTIONS OF RURAL ROADS 155 

convenience to traffic and to more evenly distribute the wheel 
wear (see premises of design, page 153). 

Widths Actually Used.— Probably the most systematic record 
of widths actually used by traffic can be found in the reports cf 
the Massachusetts Highway Commission reports during the 
years 1896 to 1900. These results were obtained under the old 
horse drawn traffic conditions and do not apply closely for the 
conditions of today. They are included in connection with this 
discussion to illustrate the change which modern automobile 
traffic has made in width requirements on the heavier traff.c 
roads. They, however, show a general relation between areas of 
light and heavy traffic on the lighter travelled agricultural roads. 

Table 19 gives the results on a few roads showing the form used 
and the variations from year to year. The footnote gives a 
summary of 160 roads and shows the results much better than 
by printing the table in full. 

Stated briefly the widths subjected to continuous wear on 
unimportant roads ranged from 8 to 10 ft.; on well travelled 
roads 10 to 14 ft. and in unusual cases 14 to 16 ft. The 
maximum widths for turn out traffic varied from 12 to 14 ft. 
on side roads and 17 to 18 ft. on the main roads. 

Modern traffic has changed conditions on the main roads but 
does not greatly affect these figures on the lighter travel roads 
up to about 300 vehicles per day. The author has measured 
similar widths on New York State main roads and found that 
they checked the widths of heavy travel of 14 to 16 ft. but 
that the maximum turn out widths were more, running from 20 
to 22 ft. This can be explained by the increase in automobile 
traffic which on account of its higher speed requires more room 
in passing. 

Even a single track pavement should have ample shoulder 
width to permit traffic to turn out and pass easily. That is the 
total width of pavement and driving shoulder no part of which 
should have a slope of more than 1 in. to 1 ft. is practically the 
same for single or double track roads. 

Effect of Vehicle Widths. — The width of modern vehicles has a 
decided bearing on double track pavement and shoulder turnout 
widths. The ordinary pleasure automobile is about 5 ft. 6 in. 
wide. The ordinary truck about 7.0 ft. wide with a wheel 
gauge of about 6.0 ft. Traffic regulations generally limit the 
width of vehicles to 96 in. except traction engines which may 



156 LOCATIOX, GRADIXG AND DRAIXAGE OF HIGHWAYS 



be 110 in. The outside wheel of any rig ought to be about a 
foot inside of the edge of the di'iving shoulder and there ought 
to be at least a foot and a half clearance between passing vehicles. 

on straight alignment and at least three feet on sharp curves. 

Table 19. — Showixg "Widths of Traveled Way 



Town or City 




^laximum w-idth of 
travelled way 



,Sli ft. 15^ 



OC .1 



1899, 
ft. 



Width of commonly 
travelled way 



1896, 
ft. 



o^ 1899, 

2-, ft. 



Athol Worcester 17 

Barre Worcester . . 

Bedford Middlesex , 15 

Chicopee Hampden. . . 

Dalton Berkshire .... 

Fitchburg (W.^ .... Worcester. . . 

Huntington i Hampshire. . 

Lincoln j Middlesex. . . 

Marshfield ' Plymouth. . . 

North Adams Berkshire 

Orange Franklin .... 

Taunton Bristol 



17 


16 


16 


15 




13 


; 15 




12 ' 


20 


I 


20 


15 


20 


20 


15 


15 


14 


15 


9 


11 


15 


15 


15 


15 


14 


12 


15 


10-12 


13 


17 


16 


16 ! 


15 


20 


20 



20 


IS 


10-12 


12 


14 


14 




9 


15 


15 




8 


20 


20 




12 


21 


16-21 


20 


16 


18 


18 


10 


10 


11 


12 


7 


8 


15 


15 


10 


9 1 


11 


12 


8 


9 


14 


15-20 


8-10 


9 


20 


20 


10-12 


12 


15 


18 


10-15 


10 



14 



14 



7 8 

10 9 

12 13 

18 12-18 

15 14 



9 
10 

7 
10 
15 



8 
10 

7 
12 

15 

r-12 



Width of traveled way on 160 roads in Massachusetts, measured during the years 1896, 
1897, 1S9S, and 1899. and printed in the report of the ^lassachusetts Highwaj- Commission 
for 1900. 

The -width of stone on these roads is given as 15 ft. wide on 130, 12 ft. wide on 3, and 10 
ft. wide on 2. It should be remembered that the stone is put on verj' much thicker in the 
middle than at the edges. 

The maximum width of traveled way as measured was as follows: 

9 ft. \^ide on 2 roads IS ft. wide on 23 roads 

10 ft. wide on 6 roads 19 ft. wide on 1 road 

11 ft. wide on 2 roads 20 ft. wide on 10 roads 

12 ft. wide on 2S roads 21 ft. wide on 10 roads 

13 ft. wide on 8 roads 22 ft. wide on 1 road 

14 ft. wide on 23 roads 24 ft. wide on 2 roads 

15 ft. wide on 30 roads 25 ft. wide on 4 roads 

16 ft. wide on 8 roads 26 ft. wide on 1 road 

17 ft. wide on 1 road 33 ft. wide on 1 road 

The width of commonly traveled way as measured was as follows: 

7 ft. wide on 12 roads 14 ft. wide on 8 roads 

8 ft. wide on 17 roads 15 ft. wide on 13 roads 

9 ft. wide on 25 roads 16 ft. wide on 2 roads 

10 ft. wide on 32 roads . 18 ft. wide on 4 roads 

11 ft. wide on 10 roads 20 ft. wide on 2 roads 

12 ft. wide on 30 roads 22 ft. wide on 1 road 

13 ft. wide on 3 roads 25 ft. wide on 1 road 

On this basis roads having much truck traffic would require a 
minimum turn oat width of about 18 ft. which is probably about 
right for the minimum width of rigid pavement on such roads 
but hardly hberal enough for total shoulder width to take care 
of exceptional cases wliich occur more or less frequently. 



CROSS SECTIONS OF RURAL ROADS 157 

Recommended Practice. — The available data obtained from 
observations on actual traffic movement indicates that a mini- 
mum turn out width of 20 ft. is desirable on single track side 
roads, 22 ft. on secondary double track roads and 24 ft. to 26 
ft. on main double track special service roads. For a triple 
line of traffic 34 ft. and a four track road 42 ft. 

From this data it appears that modern practice on single and 
double track roads requires a width of solid pavement of from 
10 to 20 ft. and a total driving width including shoulders of 
from 20 to 26 ft. 

i", i'V^ ,^, Shoulder Slope 

Crown 4 ^'^\f /f f ff-. Vfolff 



We have now practically developed a standard for the portion 
of the section used for driving (Fig. 50). The pavement that is 
to carry the heavy traffic has a specified crown for each variety 
and ranges from Y4. "to ^^ in. to 1 ft. The shoulder slope 
from the edge of the pavement to the limits of the driving width 
(20 to 26 ft.) has a slope of 1 in. to 1 ft. or possibly Y^ in. to 1 ft. 
That is, the shape of the driving portion of the normal section is 
fixed. The flexibility of the section depends on the portion out- 
side of this driving width. 

The function of the extra width is to keep the longitudinal 
drainage of surface water bej^ond the portion used for driving. 
To do this we are hmited to a minimum slope of 1 in. to 1 ft. to 
insure transverse drainage and a maximum of 3 in. to 1 ft. 
on the score of safety. It is by the good judgment of the designer 
in using various slopes between these limits and various widths 
and depths of ditches, combined with the possibilities of different 
grades that the economies in earthwork are affected and at the 
same time the design is made appropriate to the local conditions. 

Depth of Ditches (Item 5). — The author's experience indicates 
that an open ditch does not have much effect on ground water; 
that its part in the design is to drain the surface water and that if 
ground water is encountered underdrains must be used. These 
conclusions have been borne out in practice and are advocated 
by many engineers notably Irving W. Patterson of Rhode Island 



158 LOCATIOX, CRADiyO AND DRAINAGE OF HIGHWAYS 

who has had unusual success with his drainage and foundation 
designs. The principle we wish to emphasize is that deep surface 
ditches below the elevation of the bottom of the pavement foundations 
are useless. Deep ditches are not only useless but dangerous and the 
best practice calls for the least depth of ditch that mil handle the 
surface water. 

A great many road men seem to feel that a deep open ditch 
really helps drain the subgrade but as stated the author has 



>4, 

^1 Rocrc ^wau 



^ Wofher m Shoulder Soil 




never been able to prove by cases where foundation failure 
occurred that the depth of surface ditch had any well defined 
bearing on the matter provided the ditch carried away the sur- 
face water promptly. Some soils have a strong capillary action 
and the water works up through them. In impervious soils 
such as clay a surface ditch 15 ft. from the center line cannot have 
much drawing action as in numerous cases small holes dug in the 
roadbed (Fig. 51) fill with water at a much higher elevation than 
the side ditch. 



^^^^^^^ 




Frozen Shoulders ' 
Fig. 52. 




In many instances in the northern states the ground under the 
pavement proper thaws out before the shoulder material which is 
protected by a sod coating and the following result is obtained (Fig. 
52). Under these conditions the moisture in the center is held 
even in porous soils. As a matter of fact all pavement foundation 
design must be predicated on the assumption that even with the 
best drainage schemes the subgrade will at times soften somewhat 
and for this reason the use of deep ditches which are inconvenient 



CROSS SECTIONS OF RURAL ROADS 



159 



to traffic and which increase the grading cost are not in as much 
favor as in the past. 

Frequent culverts are desirable to rid the ditches of excess 
water. It should be remembered that road ditches are to protect 
the road and not furnish farm drainage and that deep farm ditches 
should be kept away from the road section. 

The following Eh ode Island standard grading sections show 
the use of the shallow 12 in. ditch which is advocated wherever 
a small amount of surface water is expected. 



J^- I <, ^ CenJ- or Grade , 



9^-- 



■. J. \(fy 



19 



l''-ii/U-/l '—>fi.-3'-->\^-^---r-SJ----r -->{<- S - >k- J->K- 4- --->!/ k-- .\ 

jVv v? I I Center Oracle ' -^ ^ l^ A 



2 .*. v-i 



\^ 



■^Ll^^-^;rr~7iv S+andard Section; Deep Ditch • J7^^^^r7?^-->«_V^, '/ 
\ ; li' ^l ^Z 7j ; -Idi 

Fig. 53. — Rhode Island standard grading sections. 

The following section (Fig. 54) represents a good typical mini- 
mum width and minimum ditch depth grading section for single 
or double track roads which has been proved by practice to be 
satisfactory where small amounts of surface water are encountered. 
This section results in about the least feasible amount of cut and 
fill in grading design for hght cuts and fills. The approximate 



^ 



\ 




i'LJ 



:^^ ,-," ^\ ■ Crown ^ fo^ to I ft 

' ^Elevation Jheorefical Gr ade \ ^ 
. ^_^, 1 y7//77V;///. 



\V' 




10 fold 

Z0'fo26 - 

24'fo28 54 

Fig. 54. — Typical minimum width grading section. 

carrying capacity of ordinary road ditches and the limitations of 
use of the shallow and medium road ditches are discussed under 
''Longitudinal Drainage," p. 262. 

Effect of Grading Width on Cost. — The width of grading from 
ditch to ditch has a distinct effect on cost but no general relation 
can be estabhshed for the ordinary road improvement where an 
old road forms the basis for the new grading. Two examples are 
given to show the value of reasonable reduction in sectional 
widths. 



160 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

1. Indian Falls-Corfu Road in New York State 
Length 1.85 Miles 
No change in profile 
No change in ratio of cut to fill 

Original Design Revised Design 

Width of macadam, 14 ft. • Width of Macadam, 14 ft. 

Width of section, 30 ft. Width of section, 24 ft. 

Depth of ditch, 18 in. Depth of ditch, 14 in. 

Original estimated excavation, 7500 Revised estimated excavation, 5200 
cu. yd. cu. yd. 

This change in section alone resulted in a saving of 2300 cu. yd. excava- 
tion or at the rate of 1240 cu. yd. per mile, or in money about $600.00 per 
mile with excavation at $0.50 per cu. yd. 

2. Pittsford-North Henrietta Road in New York State 
Length, 2.67 miles 

Original Design Revised Design 

Width of section, 30 ft. Width of section, 24 ft. 

Depth of ditch, 18 in. Depth of ditch, 12-14 in. 

Ratio of cut to fill, 1.35 per cent. Ratio of cut to fill, 1.25 per cent. 

Maximum grade, 5.0 per cent. Maximum grade, 5.0 per cent. 

Profile — Designed with straight in- Profile — Rolling grades and reverse 

stead of rolling grades and tangents vertical curves used. 

of 100 ft. between vertical curves. 

Original estimated excavation, Revised estimated excavation, 6620 

11,450 cu. yd. cu. yd. 

A saving of 4820 cu. yd.; 1800 cu. yd. per mile, or in money, approximately 
$900.00 per mile. 

The revised design on this road is a good example of what can be saved 
by the use of a section that fits the conditions, a rolling grade, and a ratio 
of cut to fill that we have found from experience to be sufficient. 



Stable Cut and Fill Slopes. — Economy of design and mainte- 
nance is affected by the selection of reasonably stable slopes. For 
the class of grading usually encountered on roads built in ordinary 
topography their effect on construction cost is not great and they 
do not generally receive much attention but for mountain roads 
cut and fill slopes are an important consideration in the design 
and their effect on cost are worth considering. 

Table 23, page 200, shows the effect in detail of various cut 
and fill slopes on yardage of the ordinary sidebill mountain road 
sections. To illustrate the point we will quote one typical case 
for say an ordinary double track section (S-14), Table 23. 



CROSS SECTIONS OF RURAL ROADS 



161 



Natural ground 


Approximate yardage per mile 


surface cross 








slope 
degrees 


Cut slope V/2 : 1 
Fill VA-.l, 
cu. yd. 


Cut IH : 1 

Fill VA : 1, 

cu. yd. 


Cut 1 : 1 

Fill IH : 1, 

cu. yd. 


5 


1,100 


950 


900 


10 


2,200 


2,000 


1,900 


15 


4,000 


3,600 


3,300 


20 


• 7,900 


7,000 


6,100 


25 




11,700 


10,200 


30 






19,600 




Fig. 55. — Example of excessively steep cut slopes. Steep grading slopes of 
this nature are a common fault in mountain road construction. 



Occasional slides can not be avoided, but continual slipping 
shows poor design and makes both the maintenance costly and 
travel dangerous. 
11 



162 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Stable slopes vary for different materials and for the same 
material under different climatic conditions. A combination of 
moisture and frost requires the flattest slopes for ordinary soils. 
On account of the great variety of circumstances affecting the 
design no hard and fast rules can be laid down but the following 
table, based on railroad and highway practice, indicates the 
slopes that are generally used. In this table and throughout 
the text slopes are referred to as 1H:1, etc., meaning IJ^ hori- 
zontal to 1 vertical. In some of the State Standard illustrations, 
however, slopes are shown as 1 on IJ^ meaning 1 vertical on 1}^ 
horizontal. It is unfortunate that an engineering requirement 
is expressed by two different methods in such a conflicting order 
and care must be taken to understand which expression is used. 

Table 20. — Stable Cut and Fill Slopes 



Material 



Climatic conditions 



Combined rain and Rain but not much 
heavy frost frost 



Arid regions not 
much frost 



Cut 



Fill 



Cut 



Fill 



Cut 



Fill 



Sand l^\[ 

Gravel I li^:l 

Loam 13^^:1 

^^">' \ 2 :l 

Boulders and earth 1^:1 

Large rock slabs extend- 
ing back into hill and 

earth 1 :1 

Disintegrated rock ! ^: 1 

Solid rock M:l 



13^:1 
2 :1 

1^:1 

13^:1 
4 :1 

13^:1 



13^:1 
13^:1 
1 :1 



2 

1 

1 
1 



34: 



2 :1 
13^:1 

mil 

3 :1 
11^:1 



1^:1 
1 :1 



2 


1 


4 




IH 




1 




m 




1 




y 4 




1 





/4 



H 



2 :1 
4 :1 

m-.i 

13^:1 
13/2:1 

1K:1 



1M:1 
1M:1 
1 :1 



Pavement Widths and Their Effect on Cost. — The hard 
pavement is the most expensive single item in a road improve- 
ment. T\Tiile it is necessary to pro\'ide a width sufficient to 
handle traffic, additional widths which merely add to convenience 
must be used with care unless the funds are practically unhmited. 
Pavement width is modified on sharp curves as discussed later. 

To give an idea of the cost of pavement width the following 
table is compiled for 1920 price conditions. The difference 



CROSS SECTIONS OF RURAL ROADS 



163 



of even one foot in width makes a large difference in cost when 
apphed to a State System and the most suitable widths are open 
to argument. 



Type of pavement 


Assumed cost 
per sq. yd. 


Cost per ft. width 
1 mile long 


Brick 


$4.50 
3.50 
3.20 
2.20 
1.80 


$2700 


Asphalt concrete 


2100 


Cement concrete 


1920 


Penetration bituminous macadam . . . 
Waterbound macadam 


1320 

1080 







Widths in Use. — Blanchard's Handbook states that in Austria 
government roads have a pavement width of about 21 ft. and 
provincial roads 14 to 16 ft. In northern France many of the 
main roads have a 15 ft. width of pavement proper with 23^^ 
ft. of stone shoulders on each side making a total of about 20 ft. 

The French national roads have a metalling width of about 
23 ft. and the EngHsh main roads run from 16 to 22 ft. 

In this country there are two sets in general use 10, 12; 15 
and 18 and 12, 14, 16 and 20. In the author's opinion the first 
wiU serve satisfactorily and is naturally more economical using 
the 10 or 12 ft. width with special stone shoulders if desired for 
secondary local service roads; the 15 ft. width with first class 
special stone shoulders on the main double track local service 
roads and the 18 ft. width for rigid pavements on double track 
special service roads. A 20 ft. width near large cities adds 
materially to the comfort and ease of traffic on commercial 
roads and is probably justified if the funds are available. For 
each additional line of traffic add about 9.0 ft. provided the traffic 
regulations permit a 96 in. width of truck body. 

There are two ways of solving the problem. The first is to 
build the strong metahng just wide enough to comfortably take 
the heavy traffic and if the natural shoulder material is not suit- 
able treat the shoulders to a width of from 16 to 22 ft. with 
gravel, crusher run or 23^-2 ^^- stone filled and rolled or if desired 
puddled or tarred making them suitable and wide enough for the 
turnout traffic. Referring to the widths actually used by hard 
traffic previously discussed this method results in the 10 or 12 
and 15 ft. widths. The second way is to make the full depth of 
metaling just wide enough to allow traffic to pass by careful 



164 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



driving not giving the shoulders any special treatment. This 
method results in the 14 ft. width on unimportant roads. The 
16 ft. width is harder to justify as on the main roads it is wider 
than necessary for moderately heavy local service travel and too 
narrow for automobile "turnout trajfic.'' Where rigid pave- 
ments are needed 18 ft. is the minimum width recommended as 




Fig. 






ilesrance, on different 



dangerous ruts develop alo::ig the edges where the 15 or 16 ft. 
width is used and even with careful maintenance this condition can 
not be avoided under heavy truck traffic on special service roads. 
Wbiile shoulder treatment is desirable on the main travelled 
roads its importance on side roads should not be overestimated. 
A record of a trip from Albany to Binghamton, Xew York. 
showed that rigs were passed on an average once every 4 miles 
outside of villages. From this it would seem that for secondary 
roads of this character shoulder treatment is not worth while even 



CROSS SECTIONS OF RURAL ROADS 



165 



for the 12 ft. width unless particularly bad soil conditions are 
encountered. Where the 10 ft. width is used solid turnouts 
should be provided at frequent intervals to allow heavily loaded 
vehicles to pass. 

In the writer's opinion 10 or 12 ft. should be used in preference 
to 14 ft. on side roads where the shoulder material is good and 
that 12 or 14 ft. with special shoulders if desired should be used 
where the shoulder material is poor. On the main local service 
roads a 15 ft. macadam is as satisfactory as the 16 ft. width and is 
cheaper under all conditions as the 16 ft. width does not overcome 
the necessity for a good shoulder. Where rigid pavements are 
required 18 ft. is the minimum width that will give satisfaction 
on double track roads. 

Effect of Curvature on Pavement Width and Shape. — Sharp 
curves modify the width and crown of road pavements. Width 
is increased to provide greater clearance between fast moving 
vehicles (approximately 3 ft.) and also to take care of the back 
wheel encroachment of long wheel base rigs (see Table 18, 
page 140). The crown is usually changed to a ''banked" or 
''one way crown" similar to superelevation of a railroad curve to 
make it easier to take the curve at reasonable speed and to reduce 
the side thrust of the wheels on the pavement and the danger of 
skidding. 

Amount of Widening. — Current practice based on experience, 
which is the safest guide, favors the following widths on curves. 




NO TE '. L encff-h of iangen -h 
runoff is approxirnahzltj 
20 X. Addifioncfl Widih in feet 
(See Table Ho.21} 



Cepterof 
Circular Curve 



Fig. 57. 



On local service roads use (Table 21). On special service 
commercial roads use Table 21 A. The pavement is widened 
on the inside of the curve. The full widening is carried around 
practically the entire curve from close to the P. C. to a point 



166 LOCATION. GRADING AND DRAINAGE OF HIGHWAYS 

near the P. T. (.see Fig. 57). The tangent runoff to the normal 
■width is made from 50 to 100 ft. long to look well according to 
the judgment of the constmctor. ThK is an easy layout to 
make in the field and serves the traffic satisfactorily. The 
widths given in Table 21 permit two outfits, each consisting of 
a 7 ft. width truck with one traiLer. to pass easily. Trucks 8 ft. 
wide without trailers can ako pass easily. The widths given in 
Table 21 A permit comfortable passing of 8 ft. trucks with one 
trailer. 

Table 21. — PA VF:\rF;> rp Wldths o>f Cusvus of LociL Sestice E,oax)S 
AJNT) S]EicoNT>AiiT State Rottteis. ' See Fig. 57) 



- ^- 


•r traok 


Lengtii 


r^angrpTit mucc i 
ft. 


29 






100 


25 






100 


23 






KXI 


22 






90 


21 






90 


20 






80 


20 






80 


19 






70 


18 






50 



50 
75 
100 
150 
200 
300 
400 
500 
€80 



Note. — Normal pavement width (15 to IS ft., used am. all enFres having a 
radios greater than 600 ft. 

Table 21A. — PATZisxT Wir)TH5 ox Citeves of ^'Bciai. Sesvtce 

CoiOCEBCXAL ROAXIS 



Kaci-is :f 



'oval pav-ement width. 

in ft. 



Length, ta.ngent ronoc 
in ft. 



100 
150 
200 

300 

300 

600 





25 


10<3 




24 


SO 




23 


90 




22 


80 




22 


80 




21 


70 




21 


70 



>. OTE. — >• nrm ;i] pavement widths c£ IS to 20 ft. used on all etcnres 
a radius greater thaa 600 & 



CROSS SECTIONS OF RURAL ROADS 



167 



Amount of Superelevation. — Superelevation of the pavement 
can not be figured as there are too many variable factors. Cars 
take easy curves at higher rates of speed than the sharper curves 
which fact tends to equahze the bank crown. The pavement 
must not be tipped enough to make it dangerous for slow moving 
vehicles. The full superelevation is carried around the entire 
curve from P. C. to P. T. and reduced to the normal crown at 



P Extra Wiolpn'ing 



C.L.of Normal Wic^ih 

■C.L.of Pa vemen f- 




NOTE: Carrcj Thcoreiical ^\ yj>\ <!, , ' 

Profile Crown Grade around o!" 
the Pavement Cenfor Line 




Normal Crown 



I . Elevafion oul'sirde edge of Pav<?menf' 

p Jo-tal 
Superelevation \ Theoretical Crown Grade 




Normcxl 
Section 



■Elevation inside edga 
of Pavement' 



150 



150 - 



Curve : 

Profile of Transition from 
Hormcxl to Bankeoi Section 

Fig. 58. 

points from 100 to 200 ft. along the tangents from the P. C. 
or P. T. The normal grade is carried around the center line 
of the pavement and the outer edge raised and inner edge low- 
ered to produce the required side tilt (see Fig. 58). 

Current practice favors the following one way crown slopes 
on curves. 

Table 22. — Table of Crown Slopes on Banked Curves 



Radius of Road Cexter 
Line in Feet 

50- 200 
200- 500 
500- 800 
800-1000 



Recommended Uniform 
Crown Slope 

13<4 in. to 1 ft. 
1 in. to 1 ft. 

% in. to 1 ft. 

yi in. to 1 ft. 



Note. — Carves having a radius of ovor 1000 ft. are not generally banked. 



1G8 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



Current Practice in Standard Sections. — The following 

Standard Sections give an idea of current practice. 

Fig, 59. — Pennsylvania. Fig. 63. — Alabama. 

Fig. 60. — New Jersey. Fig. 64. — Maine. 

Fig. 61. — Indiana. Fig. 65 — Wyoming. 

Fig. 62. — California. Fig. 66. — West Virginia. 

Figs. 67-69. — Recommended Practice. 



Header l.-?:3-Concrefe 1^ Surface Course. HeaderCurbmq 

/R,seioCrownr:§per/'/ '.^'"derCourse J--2'3ConcrSfe. 




/>^^^v' 



, 5 Concrete l-3v , „ 

7-6'- ->H -7-e-- ->^\<-6 

>j<— -.5-.'.— > 




■Id - 

—-26'- 

Header Curbing Bi+uminous Speci-fica+ion Class A Header Curbin 







Bi+uminous Specification Class B,C;D, ^ 

Radius^', J" ^ Radius i 

„ I'V \ 'Reinforcing lleia.1 .} Rise fo Crown V--I' / <:u ,i' . 

^' I ? I--2-3 Concrete \ 5" ^ 

< S^ — ->|< — 3- y< 8'- ^k 5- — -> 



Rein-forced 



Radius 4.' 



Plains 

One Couree Cemen+ Concrete. 
K .Reinforcing nTfal ^'^' ^'<jrf ace Course Mi=Z Mixture. 
4'/:^, 1 }^%Ri5eioCrown^:l .. 



Slope I i": I 



&■ • I r^Zi--5Concr^e' S /f^c//i/5f' ] ^ 

< — 



Reinforcing ,1 , Plain. 
2Q - 



Two Course Pon+land Cemenf Concrete. 



4k. 



,5" Broken Stone 



r I 



^"Macadam 



/ Rise to Crown \-\"perl / ,d Telford 



Shpe/f!/' 




i<- 5'— ->j<- 

K- ''-^-^ — 



-^— -5'— ;J 

Broken S+one Base. Telford Base. 

Water Bound Macadam. 



5 Broken Stone 



■j Rise to Crown iU-ler/' / 3'.' Telford 

^ 'MW-;L...: I ^-mi.i n.i.uual..,.i.L]i<(r...i -J_ -.,■_"" "'' " 



,3" Macadam 



:^-- 




5' — ->k 8' ^ 8'- ->|< S'- 

Broken S+one Base. Telforcl Base. ' 

Bituminous MacadanT Ffene+na+ion 
Method . 



Fig. 59. 
State of Pennsylvania. 



CROSS SECTIONS OF RURAL ROADS 



169 



Header Curbina Cr t ± xuc jdj i i'Cemenf Sand I'4 

I-0.1 r 1 2 Expansion Jomr mw Sana Bed onlu. ^^ , ,,^ , n , 

mConcrefe. .. 4^,^^^,^' s^^'mrified Block -^'"^"''''.^ ^''"'^, ^"^ ■ 

^lopeli-.i' 




s- HeaderCurbing 



'■'^^ 9.PS^^^^\ ! Rise h Croy^ni'l] 



I CemenfSand Bed 
,/•■■? Mixfure orlfSand Bed 

' M::.:z:,?Jope/irf 



6"-^ \<-\/-"-76-- ->(<"- --'--x-\-7-'5--- 

<.■ 5-0----->\<--/{-Tr^~y;ri^---j---i---/6'0->^^^^^^ }>A<r-.5:o'- 



I 



'Wood Block 




-E6-0'- 



Stone BJock 



1 



H'fo5i\Sfone 
Block 



Table Showing Distance belowCen+er ^ 
foreach'/g'yVidthPjirrfforanyCrownSW 



Table Sho' 
Curves of 



Curb. 


2" 


3" 4"\5" 


6- 


7" 


8- 


'^Widih 


I'/a" 


l%- 


B'/4 


iH 


3k- 


3h 


2 


^ » 


'/i 


*" 


r 


m' 


|y^ 


m.- 


% ,. 


'ye' 


V 


'/^ 


'/* 


%■ 


%" 


'/i' 


Ctnfer. 


0' 


0' 


0' 


0' 


0' 


0' 


0- 



wing Additional Widths of Surfacing on 

D rff e re nt Rqdii.and Superelevation per Ft. Wi dth 



Nohi: 
{ All Proporf ions for Concrete as 
I shonn on Cross-Sections are 
Subjeci-hsuch Varicrhionsas 
I are dkrted in the Specificcrl-ions. 



Radius of 
C+nLine,F{ 


Additional 
Wid+h 


30 


dO 


4-0 


70 


60 


60 


60 


50 


100 


45 


leo 


40 


140 


40 


ISO 


35 


180 


35 


BOO 


30 


^^■(? 


30 


B40 


B5 


zeo 


B5 


Z80 


B5 


300 


10 



Kind erf Surface. 


Rise per ft 
of Width. 


Vitrified Block . 


V .. 


Wood Block . 


V M 


Bi-huminousSurface 


V „ 


Concmfe Surface. 


'* » 


Slum Block. 


V* 'W 


y/aferbound Macadam 


% fo 'u " 



Nofe^ 

In Widening and SuperelevaHort 
Curves, carry ihe negular Grade 
through ontheCenterLineofthe 
RoadwaLj, and make all Wideninq 
on Inside of Curves 



Fig. 59. — (Continued) 
State of Pennsylvania. 



170 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



Standard Sections of Highways of New Jersey State Highway 

Department 



30'-o' 

.„ 0' -.1 -- 



Slopes 3 1 where fill 
does no^ ejtceed 3' 



,5, Y I -i>^r<:..l'Joini filled y^ithJoinf Filler ,. Sand Cushion 1° 4>.j£t<- | ^',\l 

a. ^j-. -.-- -| — -.-L^j.-, ' ;,.' ' ' ' ' ii;'..' \\ ' ' ' ' '^ V ' ' ' 'J. .'j { — t:~r» ;" 

i"' 4' Brick— ' <yj'-- Concreh i'}'6"-^FIaiSuhgrade 



Sar/h Shoi/yer 

Foundoflon may be 6'ihru.ci/^ BriCK 

depefrdin^ on cond, hons ^Q-Q 

'^3' =>^ J' j>-(-<-- 5' -a-t-s- 

2.V I \/^^2' i 



«/'t. 



-j^-iy.. 



Slopes 1^ 7 where fill 
ejtceeds J' 




" Concrefe I'l^-Z •10^' : 

FW Subgrede-i 
Concrete 

JO-O" 

5' -3-^- '5'.-_ 



Wit)' Subgrade 



Concrete I li' 3 8k' 







CoNCflETE 



'" 2" B'tturninous Concre^ '. " 2" Latter Clean Sfone 

S' Minimum depth macadam 

Bituminous Concrete 

, , 6ranii-eer Belgian Block 




_ Ballasi /" ig, "—■ s'mnimum depth Macadam 

'All headers IB" high 
Bituminous Concrete -Trolley in Center 

, y ' _ _ Zt ^^— ?'Joirrf Bj'^^ j'jo,ni->- j ] ^"l^" Variable j 




'2"Bituminous Concrete .. 

2"taijer of Clean Sione i'Mimmum Macadam: 10- 

BiTUMiNous Concrete -Trollev AT Side 



Fig. 60. — Typical Sections (New Jersey). 



CROSS SECTIONS OF RURAL ROADS 



171 




standard Section A 



S-0 -->f<- -- 




/ff'-O-''- 



I II 

-y<-.-5-5-- 



Standard Section B 



- -....18L0-— 



Typical Rock Section 




,11 , „ , „mi^dsm^ 

\Cru$hea\ I U 

Rock. I I 1/ ^ 



"50 



Grade cfi shown on Profile 



. 2"Crown--^ "^P'lk^^- ^lff^Pr%^. 

WWTE: S 'shoulders, used Plain Concrete 

on fills abiove 4 ' 

Gmdeas shown on Profile „ 

ConcrefeCurh ," \.^,; . ,1" Slope I per fh . , 

Monolithic wilhBase.^:. I ^ Wearing Coarse "J/ j'sinden ^I'^W ! sfZiperft 0^^ 



Wote: 



"6 Concrete Base '' 'Sub Orade Crowned ' ' „ , • ^-,>v.qi'- 

..,8LoL'. ^....sLo.'L.^...4'-o''--^ 

tys^'W""'^'J^r'^°l'''^'^''^F^^'^ Bituminous Concrete 

^.)ffp- on fills above 4' 

% Grade as shown on Profile „ 

^^Z .4"dnck ifCrown.. .w;^,/^^!,'^^'^^^ ,\\, 

V' NJ. i_ J\ olOpelper.TT. r"- ,■>" n\l4fi 

Monolithic BricK 




\.:.5^0^-^ 



Fig. 61. — Typical sections (Indiana). 



172 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



r" 
Cufin Slope. I2 5h€efAsphal-h or A&phalh'c Concrefz 

■It" 3° ^ I 5"Concrefe Baze /^///4/ 

K %■- - -T 

Type A 

I2 Asphal-hic Concrete. 

V_ 2'(v \j^ .5' Macadam Ba se. pjjj 4^1 

CufijU Slope p!!^ ^!if!L>lfij$>yji!li^ 

K- - -20'- A 

TypeB. 
^ di" si' c" e''Oil Macadam 

-y-M 1-6----^ -7-6—-+--?-^- n -^5. Tc-//,' ■, 

\k —-15- ■>^ ' ^^f^il/'z-l 

' ^ i Slope. 

TypeC. 

Cut 1 2 'I Slope :^ 

4'Concre-he Base ^.-j'Biiuminized Cushion 

A'+e^--;e^Section Type D. (^-..^yrsSftrn^') 

"^^v \ „ ^" \ Surfaced with Local Material . 

Cuth-ISIoplSSiLl. <vj__^„\.„± 

Cuflr-ISIope- %:5!X^5- i-"^'^^^K?^?V/' ' ^' 

r [<. -^i >1 ' %.5/a/7« 

TypeE. 

Ci/^ in Slope-''' '%^ v{^ ^^."2" -g,! Macadam Sur-Face^^ 2 Fill if -I 

'^1pT^i^^^^ ',iy}nnrii'niyiyu'i[ii > Vrrnf/yi!in^ Slope 

V-3-' •■>f<- 7-6'— -^ri--.-— 7-6 ->k- •^-5-->[%^ = 

K--- -/5^'-f ->| 

^°'''^' I '^4"6ravel$a5e 

The Thick neS$ of Pavemerrt stioY/n 

'ibihe M'tnimum, if so ordered bijj-he ^ p 

Highway Engineer it IS increased. ^yP® ' 

Fig. 62. — Typical Sections (California). 



CROSS SECTIONS OF RURAL ROADS 



173 



->|/-VK----6-^---->t<-- 




1":/' 



Not Cess than 
...24^0-'---- 



j^jyrrrrT /J ' />>t>>/^>'i"f/^'/>iJf^/^^/±/'f>/fr/»>>in/f/ 7: 




This Slope may t^ varied '''^'^ Section to be Used \"here Material in Excavation 
depencfin^^onClassof '^ Suitable for finished Surface 

Material in Excavation 

Hot Less finan 
^e'^ j'Oy 3-0-'->^- -4-0-'' ->^- --------- --/6-0- ->|<...4V-->k-J-<7- 





5 RoadtobeOradecfwith 
a Slight Crown ^ "to i ' 

This Section to be Used where a Natural if smaller Difth than One ^ ^ 

Mixture of Sand -Clay is Placed on a Clai^ Base shown is Sufficient use the ^ $; 

One Indicated by Do'ttedLine ^ '^ 

5 



Not Less than 
In" 



r-5: 6 tod-. \ 3-1 <. 




->|<- . 4-0 '-->Y - - - -e'-O-"- —>\ 1-6^-iff. 




~ci ' ' . -. .. 

_ . ^ ,. 7" , ,, . Road to be Graded Flat ana to 

Depth of Pitch maube ^his Section fo be Used where be Dished as shown wifhl?ead 

decreased in well Prained Sand ? ^P^^''^'' Hixture of Sand-Clay Mach by Raising Sidles and 

\s Placed on a Sand Base Lowering Cent before 

placing Sand Cla^. 



<iB^— -6-0- -•^■-4-0-^- — 

G"to8:'\ . 




Hot Less than ^^ ^, 
le'-o" >^.-4Lo''-'>^---&-0---->(l&^ 

\ I 6"tod' 



"^^^^^S^^^^r^f^^ f^Mf/M^^^ 




This Section to be Used where 
Pure Clay is Placed on a Sand Base 



/' I " I J' aI^'i I 




HotLess than 

....leLo'i 



^j^f^77r7 y>7/y^' » % ' ^>T/ -> y/'////>J7;r frh 



Cla^ io be placed L ooselj/^^ to a 
OepthofAwreximafclLi 6 'on Flat 
Subgraaeandtobe thoroughly 
mixed with Sand Base by Plowing 
and Harrowing „ „ 



\J0' 



^^fc 




. . , . • . ,. ,, ^ u Sand-hbeplaced Loosely to a 

Th,s SectiontobG Used where pepthoffrom4"tod"ontrowne 

Sand IS Placed on a Clay Base Subgrade and to be thoroughly 



Pepth of from 4 "to d "on Crowned 

Subgradeandtobe hi '-'■' 

mixed with Clay Base 
and Harrowing 

Fig. 63. — Typical sections (Alabama). Sand Clay Roads 



mixed with Clay Base by Plowing 
and Harrowing 



174 LOCATIOX. GRADIXG AXD DRAIXAGE OF HIGHWAYS 




CROSS SECTIONS OF RURAL ROADS 



175 



I II C. L . I II 

y. ll'-O- ->l< iz'-o- ->j 

L/ -rlr" J^ iLr" _ _ vj ' 

■ "+- < •■ i<isQfo Cro wn 4 to/.. 







Sechon'" A 



h 



Sfa+ion 



--iz'-o'^ 



Asphaltic Grgvgl 



+0 S+a+ion 



C.L. , „ 

,1 y-ll 



-Vj 






^^21 






Section"B" 



Biiulifhic Pavement 



^ ,0-0"fol2'-0''---^- I0'-O"fo IZ'-O 

S'-o------^ 8La'-'----> 

> Ri'sefo Crown I "fol. ' 



.^'i^s"fo9"-' ' 



W^^' 



^^^77Ai///^J/^''''C-//VP''K^ ''/>'s^//.V^^ ///~,7 



Section C 



(bravGl Track 






Station 



to Station 



C. L 




Concrete 



Station 



to Station 



¥--'/o'0%IZ'-(?'^----%----IO^(?'%tZ'-0^'--->\ 

I i ^'^<^ ^o Cro lA/n I '% /' Ul .;!i<. jj 



Section E 



Larth 




Station testation 



Lo'J. ^v^.- .foLoL' _>| 




Section F 



Earth (Machine Work) 



Station to Station 

Fig. 65. — Typical sections (Wyoming). 



176 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 




> 






ft 



f=H 



CROSS SECTIONS OF RURAL ROADS 



177 




'AUPoads shown here are 20 CtoC. ofDrhhesr ->|"B 

h %-"' --i--3'-^ 

>| / ' U- Concrete C "erf Sides, TafCenfer. "^ / ' U- 

Bev. of Thecrefical drade . 




Type I Plain. 







./4-, 



Concrete 6'af Sides, I'qf Center. 



M^M 



7/ff/ff/&>/smw/£'/imyyiy/^'V>''m!i ^^^sm 






-->| /' K- 
OnSfeepdrades 



Beinfore/nq Metal. 
Type 2. Reinforced , 




-H/'h- 



^ ^ , I I Concrete 6"at Side, 6^ 'cr^Cent^r '"' 

I L ■' 



^»>^j^&^JvyV^^?y^ 



Sloffe l" per Foof] 
Type 3 Plain. 




<— i'— >k 



Concre+e 6 qf Sides, dsof tenter 

\£^ ^M^^z,:^ L 



Wmi:p^m'jm- 



yf^rm^m'^'WT^wwmsm^^mm 



Subgrade^ Flat except at Shoulders. 

' Type4 Plain. 




Slope I" per Foot'' 



--H/'H- 



Fig. 66. — {Continued). 

Recommended Practice in Typical Sections High Type Roads. — 

The following figures illustrate the author's ideas in regard to 
desirable sections for high class roads under different grading 
conditions. 

Macadam Roads (Figs. 67 and 68) 

Single and double track. 
Rigid Pavements (Fig. 69) 

Double track. 
Car Track Sections (Figs. 70 and 71) 



12 



178 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



O'rcahr Arc Pav(?m(3nf Crown 
■■Crown Grac 



CufSlopel^U, 




^ill5lope4:f 



NOTE.y^Q fjjjc, section a ffhe top 
ofhil/s or where there i& a 
small amount- of surface water 
I'ntheolitches 



24'-0"-Y- 
Typical Section fS ha I low Ditch) 



I 

Ci 

-C: 
ft- 



---2S'-50' ^- -.-- 25-50 '- 

---So'folOO'FiGfhtofWay -,-- 

Circular Arc Pavement Crowr? ^^[ ^'^P'^ '^ '■'- 
_ XrownOra^e ^J^lif'' '"^ ^^^^' 



'Use this section where 
there is a moiderate amount of 
surface water The proper use 
^ of this section can generally 
1^ be ffleherrnine^ by inspection 



, -lOtolz'-, 
2o:o"--- 

24'to2d- > 



^^'^e^.V 



Typical SGction(Mediurn Ditch) 

Circular Arc Porvement Crown _ 
^ Cr own Oracfe 




, Special 



<- -A 7,- -, - - -> OrouncI 



Ditch 



Naiural 



Surface 



Natural interepting 
Surface 



Ditzh 



Roac^watf Proper - 

Typical Secfion (Special Pitches) 

'Where a large amount of water must be earned along fhcPoad^ 
separate the Special Ditch from the Poad Section ornol keep if as near 
the fence line as possible; this fences to reduce excavation^ saves 
Guard Rail,anal makes the Road Safer 

\ 

Bench^ut out to increase 
Distance on Curves 



'Where a special ditch is 
required the sue needed should 
t?e carefully worked out by 
means of the watershed a rea^ 
probable runoff,ana ditch 
capacity 




Fill Slope 
on High -. / 
Sidehill Fills ■%<•> 



12-^ 



V—d'-o"---^----io'-o" J 



Typical Half Section 

Deep Cuts on Grades 

less+hom5%anol Sidehill Fills 



Typical Half Section 
Deep Cuts on Orodes of 5% or more 







i/t^ "2^ 

-Natural Ground Surface _ " 'T';^ ' 
Ditch in Cut 



Typical Section (Deep Fills) 

Half Section Fills Half Section Fills 

less than 4 'Deep over 4' Deep 







Crown Gradcl 



Straight Line '/c\6f^ 

ffol Level j Grade :jJofalBank_ ^'Mcrown Grade 

\ 



2-^-3-X2 '\^—IO't6Tz'-'^^—7!-0 -'-^ 
Typical Banked Section (On Curves) 



Table of Banked Crowns | 


Radius of 
RoodC.L 


Ra+e of Bonked 
Crown 


50' to 200' 
lOO'toBOO', 

soo'tom 
soo'toiooo' 


Ik" for 

l"tol' 
i"^ol' 
ftol' 



Fiorez.- 



Single Track fiacadam Roads do noh 
have enough Traffic to warrant 
widening the Pavement at Curves 



-Single track macadam or gravel roads. (Suitable for roads carrying 
up to about 300 vehicles per day.) 



CROSS SECTIONS OF RURAL ROADS 



179 



^rown Grade 



Mdtcadam or Gravel Shoufders -, 
Circular Arc Pavement Crown „\ „ «■ 



,e 



I 

I 



|<— - 15 folG- 

22'to24-' ->l 

^. 28-0"- 

Typica! Section (Shallow Ditch) 
Macadam or Gravel Sheulders- 
Circular Arc Pavement Crown ^, 
Crown Orade 



~^<?<.. 



,vx 




d 



I8'to?o'- 

■22'to24- ----5H 

< 28' to 30 - 

Tijpical Section (Medium Ditch) 







- 5pec'ial . 
"^"Dltch"'^ 



<Oround-^- Tl/picaf Shallctv Pitch Section ->(< Ground 



Surface 



Natural 



Typical Section (Special Ditches) 



Surface 



Mercepfin^ 



DitctJ 



Non: 



Where a large amount of water must be carried along the Road^ 
separate the special ditch from the Road Section otnd keep it 
as near the fence line as possible 




Bench Cut out pf Slope on Curves 
to increase Sight Distance 



w!^^Wi^^^ 




Typical Half Section 
Deep Cuts on Grades 
less than 5% 
Concrete 
(juarcf 
Rail—-^ ..-Crown 



Typical Half Section 
Deep Cuts on Grades 
of 5 % or more \-S 




- —12^-0'-'- ->!<-—- 10-0 "-- 

Typical Sfde Hill Section 



Crown ,, ^, 
^Oracte^ 8. „• Si 

Variable 



Concrete 
GuardRaH 




Pitch in Cut- 



Half Section 
Fills less than 4' Deep 



Half Section 
Fills over 4 'Deep 



""^^^^ 



Fig. 68. — Double track macadam roads. (Suitable for local service or second- 
ary state routes carrying from 300 to 1800 vehicles per day in the summer season.) 



180 LOCATIOX, GRADIXG AXD DRAINAGE OF HIGHWAYS 



\^- — Pavernenf Proper -—'i>^ . 



' T:?. -5? yacadam 




Zrl2 



Top of Rock Excavafion 



To'p'cci; Peek Section 

Rock excavafion ¥/'■!! b<; pa id fo" fc an eisvafi'on 1 2 inches behw the surface 
of the finished rvad and no rock exca/afnon wilf be paid for befow ihis e'eyation 
croufside offhe nsaf 5'dt a'op^s shc-y/n an the pfans- 

No part of ifre sof'd rock shaH he closer than 6'nches fa the fop of the 
finished section. AH depressions, under fhepaverr?en'^p''oper lov/er than the bottom 
of the bottom course of the pav^nrenfsh^H be backfilled with stone ctrfps.fHled 
wiffl sand or gravelpind rolled or tamped unfi; firm and hard. This back f fit 
IS included in thepn'ce bid fbr rock^ excavation . j^ ^^ 







K.§^-C? ^^- I5i? fp ^/S-C --— x^^T^r/^x- r > ^ -t?^^ 

m less than 5'-0'' '='■ 
Typical 5ect!on(Sharp Curves) 



<•/ 



Jab's of ?C!~ 


Z' 


S^n-z-zz.-o-zn 


Red f us of 
Rood Ce'^-'T'- L' 
in -es*- 


r,g 


i ^0- c- 

Sj-;3-3'3vrT-":on 


5c-zc: 

100-500 
500-800 
800-1000 




:^!r.'a!fcof 



Jotal WfdH? i?T O/"/? 




r ^^ormal Width 
Additional Width 



Pavement V/idenina Lauout 



~::r : r* ^^ve"^?^* >.' C3'"'''C! 




Roa'''j& 0^ Rcac: Tc^iWidrn ■>" 


Center Line 


Paw^mznt on _ 


I'n Feet 


Curves 


5C Fee^ 


29 Fe?- 


75 V 


Z5 n 


100 " 


25 " 


200 " 


21 r r: 


5C0 » 


20 n 


400 " 


20 " 


d'j 


500 - 


19 » 


10 


€00 ' 


IS ' 


bO 


note: Use no'^^ci' °T,'enen^ Width 


on Curves havina a radius of 


more than 600'^er \ 



Table o^ PecommenolGd To\o\ DepfH of 
'iacadarT' PovenTents on Diffsrsn-f- Soils 



R7>^rTwnf in Cut or Fil ! 



So'ls 



Sand or 
3 re? '/el ! 



Loc 






--:'- 'ft deep j 



8" 



9tc2 /"f-' 

\9'to!2" !5'r3 24" 

9' \l2'tol5' 



Fig. 68. — (Continued). 



CROSS SECTIONS OF RURAL ROADS 



181 




-O 

a 
Oi 
m 

> 

o 
o 

00 



03 
O 



73 
03 
O 



P. 












182 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



Expansion 



yV'^ Expansion Jo/r}p ,RailMy Rail Channel Fiflerl^Z Mixture, 
-7"""^ Rise to Crown i''l' /! I '■•, Jifrifiedor Wood Blocks. 



i'Cemenf Sand Bed I "^'^ '^' 5"ConcVefe I'-M ^ W^' YiMfied Block Guifer 

t^MixfareorTSand Bed r'''^t'^t^^°f ,. , , Bi+""T"ous 

Construction for Single Car Track Roads. 



_ • r J. k'^o ^'Expansion Joinh .Railmij Rail Channel Eillerl-^tlix-f-ure 

fT"^"'"'''"^^- RisefoCrownfi /j \ \ ,.,-Vifrified or Wood Blocks 

■■w;'t;.E"ifc,".E 




^ks 



5')\ K- 5"Corrcrefe 5->i '<|>| \^5" 
kXemenf 5and Bed /•^•^ 

l'-4 tlixfure or I'Sand Bed Vitrified Block Bituminous 



. Concrek Buffer 



Construcf ion for Double Car Track Roada 
Fig. 70. 



^ £levation^eoret/cal_6/ rrde ^' ^ 

^Mim^M?^^--\^ 8.o---k 15.0 ' -■±-^^^ ,,.X,vmmi>i^ 

j<. J^Q .^1^ ^^^, ^ . . .. 

Fig. 71. — Car track sections. 



MOUNTAIN ROAD SECTIONS 

Discussion. — The desirable requirements for mountain road 
sections are the same as for the roads previously discussed 
but on steep sidehill work the width of grading used for ordinary 
topography would be prohibitive in cost. As most of these roads 
are natural soil roads the crown is the only element of the section 
not covered in the previous discussion. For the gravel or stony 




Symmetrical Crown 
with Guard Rail. 



One Way Crown No 
Ouard Rail. 



Fig. 72. 



material usually encountered % in. to 1 ft. is generally satisfac- 
tory. For sand or heavy soils 1 in. to 1 ft. is better practice. 
The old idea that crown should be increased on steep grades 
has been abandoned for while that expedient undoubtedly 
helped the drainage it caused more inconvenience to traffic 



CROSS SECTIONS OF RURAL ROADS 



183 



than it was worth. In many cases present practice decreases 
the crown on steep grades to give better vehicle control. Crowns 
on mountain roads are also affected by the absence of guard 
rail or other safety provisions. The ordinary symmetrical crown 
is used where wall or guard rail protects the dangerous outside 
slope but on many roads so much rail would be needed that it 
is prohibitive in cost and where it can not be used the road is 
tipped one way in a continuous slant toward the hill so that if 









^'^3 


11 


IHHi 


1 


^^^^R^^^^^~ 


- ...^ 




■ flp. 


1 


B 


Ml 






Hi^JliMKtMi 


■ 



Fig. 73. — Good example of the "one way crown' 

careful clearing. 



section. Note also the 



a machine skids it will slide in against the cut slope. This 
kind of a section is not as comfortable to ride as the ordinary 
crown but if the surface is at all greasy the element of increased 
safety outweighs any minor inconvenience of side tilt. 

Effect of Width on Cost. — The width of section has more effect 
on cost than any other part of the design. On a new side hill 
location the relation of width to cost can be roughly established. 
It will of course vary for different side slopes of the hill and 
different cut slopes of the excavation but the relation will be 



184 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

approximately as follows, for balanced sections (Table 23, 
page 200). 

Assumed 25° Sidehill Slope 
1 : 1 slope in cut. IK : 1 slope in fill 

(S- 8) 10 ft. width (ditch to outside of shoulder).. . . 4,300 cu. yd. per mile 
(S-10) 12 ft. width (ditch to outside of shoulder).. . . 6,100 cu. yd. per mile 
(S-14) 16 ft. width (ditch to outside of shoulder).. . . 10,200 cu. yd. per mile 
(S-16) 18 ft. width (ditch to outside of shoulder).. . . 12,800 cu. yd. per mile 
(S-18) 20 ft. width (ditch to outside of shoulder).. . . 15,400 cu. 3'^d. per mile 



We may say that in general a 20 ft. width requires about 3V2 
times as much excavation as a 10 ft. width. The relative cost of 




Fig. 74. — "One way crown" section. Note the ridge of earth on the outside 
of the fill. This is often done to increase safety and reduce side slip. It is in the 
nature of a wheel guard. 



different widths is also affected by the amount of rock excavation 
which is generally much greater for the wider widths. This 
depends on the depth of soil overlying the rock. This element 
affects the cost so much that in certain cases it has been found 
cheaper to build two separate single track roads for short dis- 
tances rather than one double track highway. 

Mountain roads are classed roughly as double track or single 
track, meaning the same as for railroad work, a double hne of 
traffic or a single hne with turnouts to allow passing. As each 
foot of extra width is costly it is important to determine the 



CROSS SECTIONS OF RURAL ROADS 



185 



minimum width of grading that will serve the purpose for these 
two classifications. 

Minimum Width Sidehill Section. — If the roadbed is benched 
out of solid rock a narrower width will serve as the entire width 
is firm and stable. If the section is a balanced section part in 
cut and part in fill it must be wider as embankments on steep 




Fig. 75. 

slopes are liable to settle, slide or washout and it is not safe to 
drive as closely to the edge as in the first case. The amount of 
the road ''in sohd" is therefore the prime requisite and . . 
''ft. in solid" is often used as the specification for contract road 
jobs where engineering design is not used. Present practice 
favors a minimum single track, total grading width of 10 ft. in 
rock or where the outer embankment is sustained by a retaining 

\ 




CASE NO. I. 

All"ln Solid' 




CASE 2. 
.PartCu-h- Part Fill. 



Fig. 76. 



wall and a total width of 12 ft. for the ordinary balanced section 
in earth. Balanced sections are generally used up to 30° side 
slopes and beyond that toe walls or retaining walls are necessary 
for earth sections. For a 30° side slope a total grading width of 
12 ft. results in approximately 7 to 8 ft. in solid cut. A double 
track section requires a minimum total grading width of 14 ft. 
in rock or wall sections and 16 ft. in balanced earth section which 



186 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 




Fig. 77. — Narrow single track through cut section. 




Fig. 78. — High turnpiking (gravelled) with deep ditches to raise road on flat 

above spring floods (Utah). 



CROSS SECTIONS OF RURAL ROADS 



187 




Fig. 79. — Ordinary mountain road turnpiking (Colorado). 




Fig. 80. — Simple turnpiking in easy location Targhee national forest (Idaho). 
Note the comparatively narrow width of clearing for small Jack Pine growth. 



188 LOCATIOX, GRADIXG AXD DRAINAGE OF HIGHWAYS 




Fig. si. — Temporarj- timber cribbing to hold fill. 




Fig. 82. — Example of ordinary- rough rubble retaining wall section. 

Note. — This is not first class work as the face of the wall is too nearly vertical. 
A larger face batter is desirable. 



CROSS SECTIONS OF RURAL ROADS 



189 



gives approximately 10 ft. in solid. These same limiting widths 
apply to turnout sections on single track roads. Where guard 
rail is used 1 ft. should be added to these widths. These widths 
are, however, very skimpy and if the money is available at least 
2 ft. additional should be used. 




Fig. 83. — An example of poor unsafe wall construction. 



Turnouts. — On single track roads turnouts are constructed at 
sufficiently frequent intervals so that drivers can see between 
them and there will be no danger of meeting at impassable spots. 
This generally requires from 5 to 10 to the mile. The minimum 
satisfactory length of turnout is about 60 ft. and the grade should 
be as easy as possible at these points. 



190 LOCATION, GRADING AND DRAINAGE OF HIGUWAYS 







f • Mj|^|d^9|^^^^^H 






M* ^^^^' 






^^H 


' 




^HHHHhI all 




i 


I^H 


n 


■ 


in 


- oO 
c 

ho 




■ 


V, 




i^^H 


i ' 




"W^f ^^H^^^^^I^^^H 


y 




' ^^Hl 


Mf^ 




iHl 


i^mii^, . 


^^ 




1 










0) 

,i3 



o 



'73 
O 



O 



a> 




> 












C/J 




© 




-C 




-t^ 


d 




bfl 


o 


to 


Oi 


'^ 




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CROSS SECTIONS OF RURAL ROADS 



191 



Fill Sections. — Through fill sections must be constructed wider 
than sidehill sections as the sides are bound to slough off under 
weather action and all the elements of wear tend to decrease the 
width ; 14 ft. is considered the minimum width for a single track 
road and 20 ft. the minimum for a double track. A symmetrical 
crown is advisable on fills even on curves. Where guard rail is 
used increase these widths 2 ft. These sections occur on only a 
small per cent, of the length of mountain roads. 




Fig. 85. — "Bench section." 



Through Cut Sections. — These sections are rare in occurrence; 
the minimum width, ditch to ditch, for single track roads can be 
considered as 12 ft. and for double track 18 ft. The use of 
minimum widths for either through cut or fill sections on moun- 
tain roads has small effect on cost and for that reason more 
liberahty in their widths is allowable. 

Turnpike Sections. — ^ Where the natural ground cross slope is 
less than 5° turnpiking is the usual construction and the difference 
in cost of a single or double track is so small that it is not worth 
considering. For this class of section a minimum of 22 ft. be- 



192 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

tween ditches will apply to any road and a width of 24 ft. is 
generally used. 

Selection of Section. — Plate D, pages 194 to 199, illustrates 
typical mountain road sections, pioneer districts. 

The turnpike section is used up to natural ground side slopes 
of 5° for continuous balanced work. 




Fig. 86. — Tunnel section. 



The sidehill sections are used above 5° for continuous balanced 
work. The one way crown is used on all single track sidehill 
sections where guard rail is lacking. The one way crown is used 
on unprotected double track roads where the side slope is greater 
than 15°. The symmetrical crown is used on protected double 
track roads and on unprotected sections where the side slope is 
less than 15°. 

Through cut and fill sections are used where required by the 
profile. 



CROSS SECTIONS OF RURAL ROADS 



193 



Superelevation is used on curves in cut but rarely on high 
through fills. The ditch on the upper side of a superelevated 
through cut section can be omitted if the cut is short. 

Cut and fill slopes depend on the natural material and climate 
and were discussed on page 160. There is too much tendency 
to use steep slopes to save on construction cost although exces- 
sively flat slopes are not necessary or advised, it being cheaper to 
take care of minor shdes by maintenance. (For effect of cut 
slopes see Table 23, page 200.) 







Fig. 87.— Half tunnel section. 



Wall Sections. — ^These sections are used where the natural 
hill slope is practically as steep or steeper than the stable em- 
bankment slope. Toe or retaining walls are necessary for earth 
embankments where the natural slope exceeds approximately 30° 
and for rock fills where the natural slope exceeds approximately 
40°. Wall details are described in Volume II and III. Sur- 
charged breast walls are to be avoided if possible. 

Intercepting Ditches. — Where considerable water runs down 
the uphill slope intercepting ditches are used to protect the cut 

13 



194 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

slope and relieve the road ditch of excess water. These ditches 
discharge to the nearest cross culvert and are an important part 
of the design. 

Bench Sections. — ^Bench sections are used in rock ledge work. 
(See Sections S-10, Plate D, and Table 23, page 208.) 



Pl-^te D. — MorxTAiN PIO^^:ER Roads. 



Typical Super-Eleva-hed Sections on Curves. 

Never use a Super- Eleva+ed Section where the Inside 
o-ffhe Curve is on a Dangerous Downward Siope. 
Use Super-Eleva+ions onlu on Curves iiavinqa Radius 
LessfhandOO-H-. Use the same Super-Elevation on dOO-Ph 
\ Radius Curves as on 100' Radius Curves. 
Ttie Cen+er Line Elevation and Portion otthe Section 
on the Inside ot the Curve remains Norma 1^ the Portion 
of the Section on the Outside otthe Curve is changed 
as indicated below. 




C.L. Croivn 



Typical Super-EI-eva+Jan 
In Fill. 




'j^ll!£:§/I£^S^. 



Sfandord Depth 



■ypical Super-EIevcrl-ion 
In Cut. 



CROSS SECTIONS OF RURAL ROADS 



195 



Plate D. — (Continued) 




Typical Turnpike Sec+iona 
Designated T- Section. 



r^-f"' — 

Crown Elevafion\ 16" 



-/?' 



->)<— 5'--H 



Crown 
Elevafion 



Section T-12 

Crown|-"tor 
•4 



,e' — 




H-5— >j 



CLProfile Oracle 



Section T-i6 
Crow n^ to r 



^.;.5'-..><. 



Crown E!>evafior7 



—t20'- 



->|<— iT— i 



7-" 



WWfmm 



C.L 

C.L\Profile 6\acle 



I C.Z. 

'Wrofll 



mw 



Section T-20 
Crown^"to l' 



//a^e- 



)Wr«r« 5/Vs'^ Slopes lie between 5 Deg.and iSDeg 
use a Combination of 5 and F SecfionSy usina 
J 5 Sections in the Cut Side and -^ F Sections 
onthe Fill Side-r 



No+e: 



Use Turnpike Sections on Slo-pes up to SDea. 



196 LOCATIOX, GRADING AXD DRAINAGE OF HIGHWAYS 



Pi_iTi; D. — (C&ntinued) 



Typ.cc:; . "-cc-. -. . Ssc-.ona 

Nafei Fin 5lopes /'I Rock Fills. 

I^'t Ordinary Earth. 
I^^l Special Cases. 

tfffli^e Yeasts excavation oj ~>afrsnirKi 
Slopes in Fills. 



CLoF Crown 

Ele.vo'^ion . 







CJ. of Crown 
£leva^ior?^^ 








CROSS SECTIONS OF RURAL ROADS 



197 



Plate D. — (Continued) 



Typical Side Hill Sec+ions 
tlotg: Designa+ed S Sec+ion&.. 
'use these Szcfions on I lj where Side Slope 

is greater +han 15 Deq. 
1 On Side Slopes between SDeg. and l5Deq. use 

Tr/o-Wau Crown, except in Section 5-TO. 



Frequent- Turnout- Widen in as must be 
used with this Section. 
Section 5-d is -the Mini mum in Rock. 
Section S-IO is the Minimumm Earth, 




One-Way Crown^tdl 
Wherever Short Radius Curves are necessaruj around a Spur anditis 
impossible i-o see ahead well, use this Section. 



198 LOCATION, GRADIXG AND DRAISAGE OF HIGHWAYS 



Plate D. — (Continued) 

Typical Through Cu"!- Sec-i-ionei 
Desfgncrhed C Sections. 

M>fe-- 'Cirf- S.'opes;^ -7 /n Rock 
, '? '' ' °'- Ordinarjj EaH-h 

2'l Disird^rafed Rock. i^ -. I SozciaJ Soils 

I^IBouldsja'-dE::'^r ,,, OneSri^ep S^cfe Hills whtr^ the Use 

|-/ Lar^e o::-c:s-^-e ^, s^ ^ ,^ .-; ^^Idmake 'jrr^asorable 

and Earth. LonqSkjpe. 

Sec- c- Z- 
C-C--.-4'- 

Sec-.c C-,2. 

Crc-.-i-.' 

W.^u ^^' j»^:^ 



5' -»-^-^ 






*^ ? 5i^5C7^ 



SecTion C-16. 
•/5' — 




Secricr: C-!& 
Crowr. S'-hsl' 



CROSS SECTIONS OF RURAL ROADS 



199 



Plate D. — (Continued) 



Typical Wall 6ec+ion 
Double Track Road. 
Minimum Wid+h, 



Seo+ion W-12. 



• hS'fo2.0' 




NOTE, 
yfall generality dnj 
rubble masonrij. 
tfsubjecffo creek 
wash, mor+ar rubble 
or concrete. 

Face baitero-f- 
d'fo 



•f Drtj Rubble -^ O.S'h U -- 



Typical Wall Sec-Mort. 

Single Track R.oad. 

Minimum Wid+h. 

Section W-8. 



Wall Sec+ions. Designated W. Sections. 



200 LOCATION, GRADIXG AXD DRAINAGE OF HIGHWAY 



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202 LOCATIOX, GRADIXG AXD DRAIXAGE OF HIGHWAYS 



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a 03 4* 


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11 




"2 


d d p. i; 


C! 


Vj2 o ft 


bo :3 (U w^ 


d 


cH 4,15 




< 




rt ^^^ 



206 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



























































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\ \ 










1 















\ \ 






\ V 

















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A \ 1 


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P 


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1 




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h\ 


V 
















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i 


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V .y 



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ft - 

CO CO 



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03 ei £4 1-I r4 



CROSS SECTIONS OF RURAL ROADS 



207 



Table 23. — Approximate Quantities Wall Section Minimum 
Single Track Road Section W-8 
Double " " " W-12 



1.5 or 2.0 




TYPICAL SECTIONS 
30° & 35° Slopes 

Ditch Excavation Makes 
Fill Back of Wall 



TYPICAL SECTIONS 
40 & 45 Cross Slopes 
Borrow Fill Required 



Note. — Rough rubble masonry walls to have outside face batter of 3" to 
l' and a bottom width of 3^ the height. The foundation to be carried to 
a firm strata. 



Natural 

Ground 

Cross 

Slope 


Approximate Quantities per 100' of Road for W-8 Section 


Wall 
Masonry 


Ditch 
Excavation 
Used in Fill 


Borrow 

Excavation 

for Balance 

of Fill 


Wall. 

Excavation 

Waste 


Total 
Excavation 


•30° 

< 
45° 


46 cu. yd. 

55 " " 
100 " " 
135 " " 


55 cu. yd. 
80 " " 
30 " " 
45 '* " 


None 
None 
90 cu. yd. 
100 " " 


IS cu. yd. 
20 " " 
35 " " 
45 •• " 


70 cu . yd. 
100 " ** 

155 " " 
200 '* " 



Table for Minimum Double Track Section W-12 



Natural 

Ground 

Cross 

Slope 


Approximate Quantities per 100' 


Wall 
Masonry 


Ditch 
Excavation 
Used in Fill 


Borrow 

Excavation 

for Balance 

of Fill 


Wall. 

Excavation 

Waste 


Total 
Excavation 


•30° 

K 

K 

45° 


65 cu. yd. 

90 •• " 
180 •• •• 
250 " " 


100 cu. yd. 

140 " " 

30 " " 

45 " " 


None 

None 
200 cu. yd. 
250 " " 


IS cu. yd. 
20 " " 
45 " " 
80 " " 


IIS cu. yd. 
160 " •• 
275 " " 
375 " " 



Note. — Above 45° ground slope use Rock Bench Sections, except in un- 
usual cases. 

• Retaining wall section on 30° cross slope is not usually economical. 



208 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Table 23. — Table of Approxlviate Quaxtitles Road 
Benched out of Rock 




TYPICAL SENCH 

SECTION 



Using S-8, S-io, S-12, S-14, S-16 



Natural 

Slope of 

Face of 

Rock 

Ledge 



Cut 
Slope 



Approximate Excavation in Cu. YcL per loo'' for 
Different Sections 



*S-S 



S-io 



•S-12 



S-14 



S-16 



50° 


yi:i 350 cu yd 500 cu yd 


660 cuyd 


870 cu yd 1,100 cu yd 


60° 


>i:i 600 " " 850 " " 


1.200 " " 


I.5SO " " '2,000 *• *• 


70° 


Vertical 560 " " 800 " " 


i.oso ** •' 


1,400 " •• 1,800 " " 


80° 


Half |46o " " 550 " " 680 •• " ' 




Tunnel | I 1 



• Minimum width single track in rock. 
•• Minimum width double track in rock. 



Summary of Sections. — The Standard Sections in current use 
are generally well designed but their use in actual design is too 
uniform and mechanical. That is, considerable needless gi-ading 
often results from the failure to vary the section shape to conform 
to short special local conditions. This point is taken up in detail 
in the third book of this series and results in noticeable con- 
struction savings. 

Ditches are also often needlessly deep and dangerous and fail 
to regulate ground water which is the only excuse given for their 
use. The use of road ditches for farm drainage is poor poUcy. 
Any system of special farm drainage should be separated from 
the road design except in the matter of culvert elevation. 

Right of Way and Clearing Widths.— The width of Right of 
Way is determined by required grading widths, by required 
clearing widths, by possible futm-e widening of the gracUng and 
by a minimum sight cUstance where buikUngs may be erected 
directly on the road boundary or where a heavy stand of brush 
or trees grow on the land back of the road boundary. While it 



CROSS SECTIONS OF RURAL ROADS 



209 



is desirable to provide sufficient width for all the requirements 
of the future the use of a needless width results in waste land 
which might better be utilized for farming or building purposes. 
There have been cases of rights of way 500 ft. wide in flat country 
which were merely ridiculous. 




24'fo32'- -J 

60 +0 70 Minimum 

Fig. 88. 



J 



The ordinary double track improved road section varies from 
24 ft. to 36 ft. ditch to ditch. The cut and fill slopes back of the 
ditch line rarely take up more than 10 ft. in ordinary topography 
and experience indicates that a 50 ft. width of right of way will 
as a rule be satisfactory as far as the grading of the ordinary 
rural road is concerned. Practically all engineers are agreed 




Fig. 89. — Parallel rows of trees, uniformly spaced, make for attractive 
roadsides. A state highway near Lenox, Mass. Note also shallow ditch and 
the safety of this entire roadway. 

that tree planting and sidepaths for pedestrians are only a matter 
of time and that an allowance for improvements of this kind are 
reasonable. Such an allowance would naturally increase the 
normal right of way width for the usual local service road to 
approximately 60 ft. 

14 



210 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

On. State and National routes where four lines of traffic are 
anticipated a normal width of 80 ft. ought to serve satisfactorily 
except as modified for deep cuts and fills, sight distance on sharp 
curves and clearing widths. 

Modifications for deep cuts and high fills show up on the cross 
sections. Modifications for sight distance can be worked up 
diagrammatically for each case but in order to give some idea of 
the approximate increase in right of way widths for sharp curves 
the following tables are inserted. 



Table 24. — Table of Distance Between (^ of Road and Right of 
Way Line on the Inside of the Curve to Permit Certain Specified 
Sight Distances Assuming that the Line of Sight is not Ob- 
structed Within the Limits of the Right of Way and the Curve 
IS Longer than the Sight Distance Required 



Road center 

line radius 

in ft. 



200 ft. 
Sight distance 



300 ft. 
Sight distance 



400 ft. 
Sight distance 



500 ft. 
Sight distance 



Values given below are the distance from the road center line to the 
right of way on the inside of the curve to give the sight distance 
shown at the head of each column. 



100 


100.0 










150 


38.0 


150.0 






200 


26.8 


64.3 


200.0 


..... 


250 


20.8 


50.0 


100.0 


250.0 


300 


17.1 


40.2 


76.3 


134.0 


400 


12.7 


29.2 


53.6 


87.6 


500 


10.1 


23.0 


41.8 


67.0 



Table 25. — Table of Radii of (^ Required for Different Sight 
Distances and Different Right of Way Widths Assuming that 
the Line of Sight is Tangent to the Right of Way 
Line. — This permits building being erected on the line. This table 

indicates minimum curvature for certain limiting right of way widths 

metropolitan districts. 



Total width of 

right of way in ft. 

_(L of road located 

in center of right 

of way 



200 ft. sight 
distance 



300 ft. sight 
distance 



400 ft. sight 
distance 



500 ft. sight 
distance 



Values given below are the approximate radii in ft. of the road (^ 
to give the required sight distance 



50 


212 


463 


812 


1262 


60 


182 


390 


682 


1056 


80 


145 


301 


520 


801 


100 


125 


250 


425 


650 



CROSS SECTIONS OF RURAL ROADS 



211 



Modifications for clearing depend on the height and thickness 
of the growth. The object of clearing is first to remove growth 
within the slope lines, second to provide a clear view and third to 
clear sufficient width to allow the sun to reach the road, dry it 
out and melt snow. This last depends a good deal on the direc- 
tion in which the road is running, the altitude and geographical 
location. It is entirely a matter of judgment (see Figs. 39, 
page 139, and 80, page 187) but should be liberal in the forest 
districts and ranges from 30 ft. in low growth to 150 ft. in adverse 
locations and high growth. In high altitudes roads are at their 
best closed in winter and if careful location and liberal clearing 
will increase the length of the open season it is well worth while 
as in effect it increases the usefulness of the road by 15 to 25 
per cent. 

Recommended Practice. — All the evidence seems to indicate 
that the following normal Right of Way widths will be satis- 
factory provided they are modified for unusual conditions of 
grading, sight distance and clearing. 



Main routes, 
ft. 



Secondary roads, 
ft. 



Local roads, 
ft. 



Mountainous regions 
(cheap land) 

Farming country (moder- 
ately cheap land) 

Metropolitan districts (ex- 
pensive land) 



150 
100 

80 



100 
70 
60 



100 
50 

50 



CHAPTER VI 



DRAINAGE 



The success of any road depends largely on an effective drain- 
age design. The fundamental idea underlying the various 
schemes is to prevent ground water from reaching the subgrade 
and to get the surface water away from the travelled way and 
out of the longitudinal ditches as soon as possible. 



^Mi^m. 


.Jill Smi^ .kih ' 






t ■* -'*yBH^^5^S 


wBBI^Sbp^^' 



Fig. 90. — Undrained road conditions (Wyoming). 

The problem of drainage may be divided into three parts : 

1. Cross Drainage. 

2. Longitudinal Surface Drainage. 

3. Underdrainage. 

1. Cross Drainage includes Culverts and Bridges located at 
natural stream, crossings, natural swales, artificial drainage or 
irrigation ditches, low points on the road profile, equahzing 
culverts where the road passes through a naturally depressed 
sump area, overflow culverts in flooded areas and ditch relief 
culverts on long grades. 

Long span bridge design is a speciahzed subject and no attempt 
is made to discuss it in a book of this kind which will only con- 
sider culverts and small span bridges. 

212 



DRAINAGE 



213 



The points to be considered in culvert and bridge design are: 

(a) Location of structure. 

(6) Area of waterway. 

(c) Slope and elevation of inverts. 

{d) Design strength for dead and live loads. 

{e) Length of structure. 

(/) Economical type of structure. 
If the funds are hmited the cheaper types may be used but all 
necessary structures must be built not only to protect the road 
but to establish a reasonable drainage scheme which is recognized 




Fig. 91. — Temporary timber box culvert (Utah). 

and becomes fixed by usage as the country develops; it is very 
difficult to change surface drainage in well settled districts without 
annoying and expensive lawsuits. 

Justifiable economy in culvert and bridge design lies very 
largely in the selection of the most economical type of structure. 
This is important and well worth while from a money standpoint. 
The omission of structures, reduction of reasonable waterway, 
dangerous shortening of length, weakness for reasonable modern 
loads or high waterways causing ponding are poor economies. 
For high class macadam or rigid pavement roads, the cost of 
ordinary culvert work exclusive of long span bridges does not 
generally exceed on the average over 3 to 8 per cent, of the total 



214 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

cost of the road indicating that liberality in the essentials of design 
do not add noticeablv to the total cost of a general road system. 
(a; Location of Structure. — Poor location of stnicnires is the 
most prevalent fault of the usual road dra^agie scheme. A good 
location fulfils the fundamental req[iiirem.ent of getting the water 
across and away from the road as soon as possible. It also con- 




siders the desirability of a fairly uniform Telocity of flow d the 
water in the channel and through the stnictiire in order to 
minimize scour or silting up of the waterway. Sharp changes <rf 
direction in the flow of water are undesirable. 

SIMPLE ILLUSTRATIONS OF CULVERT LOCATIOT^^S 

Case I. — Simple right angle stream crossing (Fig. 93 . There 
is never any doubt in this case. The structure is placed directly 
in the stream line and at right angles to the road center line. 

U — ^' — "iO'-n C^^^^^l 



- 


C.L.'' ^-::>-^.. 




- 


- 


? - ~ ■ 


Pig 


-i-5 — 5^-- :-cr"-?! 

. 93 . 



Case n. — Stream crossing on skew angle Fig. 94). In a ease 
of this kind it is desirable to place the culvert in line with the 
natural stream channel. 



DRAINAGE 



215 



The right angle location marked ''Poor" saves length of 
culvert but generally requires four sharp changes in direction of 
flow which tends to check the velocity of flow and to produce 
scour and silting up at the angles. Considering maintenance 
costs it is generally poor economy unless the creek channel can 
be changed for some distance. 



Umuaual relocah'on c^fChomnely 



'—■Ooo(p{ Location 




-Usual 3hat-p^ angle 
c^itch location 



—Foor Location 



Case III. — Where stream must be carried along road for some 
distance (Fig. 95). The location marked "Good" gets the 
water on to the low side of the road as soon as possible, minimizes 
sharp changes in the direction of flow and is desirable unless 
houses or barns are located on the low side of road between where 
the stream strikes, and leaves the road. 



^ Fenc3 



Notrnore than 
'/ 45° Angle 




CL. of Road ^ 
Good location Culvert Ho. I 



Fig. 95. 

Location No. 2 is desirable where houses are located on the low 
side of the road but not on the high side. 

Location No. 3 is not desirable under any conditions as it 
checks flow and causes trouble by reducing the culvert capacity 
and encouraging scour and silting. The author has a number of 
cases in mind where locations of this nature have proved very 
unsatisfactory. 



216 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Case IV. — Ditch relief culverts on side hiU location (Fig. 96). 
Ditch relief culverts on side hill locations are very desirable as 
they minimize ditch scour. They are placed at any natural gully 




Prof 



,■■ Fence 



45 Skew 




Fence 



-Spacing of Culverts- 
Tig. 96. 



formation and on uniform slope formations are spaced from 300 
to 500 ft. 

The spacing between these ditch rehef culverts on sidehill 
locations depends on the grade, soil, ditch Hning and width of 





Fig. 97. — Open slat top relief culvert. Xote angle with Q_ of road. Pioneer 

road Colorado. 

section. A narrow 10 ft. mountain road requires more relief 
than a 20 ft. road in the same location as even a small washout 
will put the narrow road out of commission wliile a moderately 



DRAINAGE 



217 



bad ditch scour will not stop traffic^ in the second case. No set 
rules on spacing can be given but current practice favors ditch 
relief culverts on 8 per cent, grades at intervals not exceeding 300 
ft. and on 5 per cent, grades not exceeding 500 ft. If cobble gutter 




~, ^Vv^.vi>-^ 



Fig. 98. — Typical inlet (mountain road) for pipe ditch relief culvert. 

or concrete ditch Uning is used the distance can be materially 
increased but is not advised. On long cut and fill hills drop 
inlets into storm sewers are sometimes necessary to prevent 
overloading of the ditch. 



Main Road 



Macadan 



SJde Cuk in Ditch Line 



Side Culvert Set 
Back on Side Road\ 




Fig . 99. 



Case V. — Side Culverts (Fig. 99) . In designing culverts under 
side roads, the length must be great enough to provide an easy 
turn for traffic; many times a saving in length can be made by 
placing the culvert a short distance down the side road as shown 



218 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

in Fig. 99 but this should of course not be done on steep 
grades. 

Don'ts. — The main fault to avoid in the location design of 
culverts and bridges is the use of the right angle location where 
this is not the natural and reasonable layout. The right angle 
layout is desirable on account of economy where it fits the con- 
ditions. 

Do not omit culverts on side hill locations and run the water 
for long distances in the road ditches. 

(5) Area of Waterway. — The size of opening is usually deter- 
mined by noting the size of the old structure or, if none exists, 
the size of other structures over the same stream and by inquiries 
of neighboring residents or the road commissioner as to how the 
existing structure has handled the water in the past. As a 
general rule the size of opening or span should not be reduced 
below that of the present structure but in the case of steel 
bridges that have been sold to town boards by enterprising 
bridge companies it is often found that the span is needlessly 
long. The evidence of existing structures is the most reliable 
basis of design but the conclusions should be checked theoretic- 
ally and for small drainage areas in villages and all drainage 
areas affecting new locations in sparsely settled districts either 
the physical evidence of high water or some maximum run off 
formula must be used. Run off formulae are based on the rate 
of rainfall, area of the watershed, topography and soil. The 
rate of rainfall varies for different geographical locations and the 
length of the storm. Reliable information for any locahty can 
be obtained from the weather bureau. Short storms develop 
the greatest intensity and produce the largest runoff for small 
watersheds. The rates reached by these storms should be con- 
sidered in designing ditch relief culverts or cross culverts with 
smaU drainage areas. A liberal basis for these cases is the 5 
or 10 minute duration rate of Table 26, page 220, Table 27, 
page 221, illustrates the method. Most culvert design is based 
on a 24 hour precipitation as illustrated in Table 28, page 222, 
and applies to watersheds of say 0.5 sq. mi. and up. Streams 
requiring structures of over 10 ft. span generally produce phys- 
ical evidence of high water which can be safely used. 

Table 30, page 224, gives the size of opening used by the 
Santa Fe Railroad; Table 31, page 226, gives the size of opening 
for small culverts used by the New York Central. Table 32, 



DRAINAGE , 219 

page 226, gives the size of culvert used by the Iowa Highway 
Commission. These tables serve to illustrate the application 
of this principle of design. 

Weather bureau records show maximum 24 hour precipitations 
of 7.66 in. at Portland, Oregon, 5.12 in. at Los Angeles, Cali- 
fornia, 2.06 in. at El Paso, Texas, 7.03 in. at Kansas City, 
Missouri, 9.40 in. at New York City and 8.57 in. at Savannah, 
Georgia. These rates are rarely used for runoff computations as 
they represent extreme cases of rare occurrence. Good 
practice uses a 24 hour rate of from 4 to 6 inches. Openings 
based on these rates where the culvert will handle the water 
without quite running full will take care of unusual cases by 
the forced discharge due to the formation of a shallow pond 
on the up stream side of the road. 

Examples of Use of Tables. — Table 29, page 223, gives 
the normal discharge of small culverts laid at different rates 
of grade. To illustrate the use of Tables 27 to 32 three 
examples will be given. Suppose water from 2 sq. mi. of flat 
farming country in the North Atlantic States is to pass through 
a culvert having a natural slope of 0.5 ft. to the hundred. 
Table 28 is figured for a 4 in. rainfall in 24 hours which is 
reasonable for this section. This table shows a runoff of 334 
second ft. for flat farm land. For a slope of 0.5 ft. per 100 
table 29 shows that a 5 ft. X 5 ft. culvert will carry the water. 

Suppose we have steep rocky ground of say 200 acres or J-^ 
sq. mi. in Oklahoma and a culvert slope of 2 ft. per 100. The 
best data is the Sante Fe Table 30 which gives an opening of 
51 sq. ft. at 10 ft. per second or a run off of 510 second ft. Table 
29 shows that a 5 X 4 ft. culvert on a 2 per cent, grade will 
carry this but that the velocity is" high and the culvert must have 
a soUd bottom and riprap protection at both ends. Where pipes 
or solid bottom culverts are used high velocity is not objectionable 
but where the bridge type is used a sufficiently large opening 
to keep the velocity down to 10 ft.' per second or less is 
advisable. 

Suppose a ditch relief culvert drains 2 acres in the cloudburst 
region and can be laid on a slope of 3 ft. in a hundred. Use 
last column Table 27 which gives 12 second ft. which from Table 
29 gives a 16 in. pipe. 

Practical Considerations Governing the Size of Waterway. — 
For moderate sized drainage areas the culvert opening is pro- 



220 LOCATIOX, GRADIXG AXD DBAIXAGE 



TS 



bigli. a. fain, as 11 in. in. 1 L: 
iw- areas ^Mmld. be made s' 

: :z?"^:r=- ^ee last eofcz; 
11 iz. " : f TJaawKr - : : r i: 



'.Sl 






tfcT'; 



Beet.:- .' 3.I5S 



Detroit^ Mkii. 
DuhitiiL :i^^ 

IfihraiLz T 

Xew- Orle.i^. 
NcKfidk, Va.. 
Oknaha^ Xdb. 



---3.^. 



DC... 




5.0 
5.9 
3.7 
3.3 
6.0 
2.4 
3.6 
7.1 
4.2 



3.5 
4.8 
4.0 
6.0 
3.8 
5.1 



l.o 
1.7 
1.6 
1.1 
1.2 
2.2 
1.4 
2.6 
2.2 
1.3 
1.9 
2.2 
1.6 
1.6 
1.5 
2.2 
2.3 
1.8 



DRAINAGE 



221 



Table 27. — Maximum Runoff. Small "Watersheds 
Burkle-Ziegler, Sewer Formula 



4 



Av. slope of ground in feet per 1000 



No. of acres drained 



Cubic feet per { Av. cu. ft. rainfall 1 X 

second per acre = C X j per second per acre > 
reaching culvert. [ during heaviest fall. J 

C = 0.75 for paved streets and built up business blocks. 
C = 0.625 for ordinary city streets. 

C = 0.30 for villages with lawns and macadam streets. 
Assumed C = 0.25 for farming country. Note. — This value is high from the standpoint 
of sewer design but culverts are short and might better be liberal in size. 
One inch of rainfall per hour equals 1 cu. ft. per second per acre. 





Discharge i 


[N Cubic 


Feet per Second 










Rate 


of rainfall 4 in. per 


hour 


! 


^Assumed 
















Runoff steep 


Area 














stony moun- 


in 


Fall 5 ft 


. in 1000 


FaU 20 ft 


. in 1000 Tall 50 H 


.. in 1000 


tain slopes 


acres 


















C = 0.30 


C = 0.25 


C = 0.30 


C = 0.25 


C = 0.30 


C = 0.25 


Rainfall 8 in. 
per hour 


1 


1.8 


1.5 


2.5 


2.1 


3.1 


2.7 


6 


2 


3.0 


2.5 


4.2 


3.5 


5.4 


4.5 


12 


3 


4.1 


3.4 


5.7 


4.8 


7.2 


6.0 


18 


4 


5.0 


4.2 


7.2 


6.0 


9.0 


7.5 


23 


5 


6.0 


5.0 


8.5 


7.1 


10.7 


8.9 


28 


6 


6.8 


5.7 


9.7 


8.1 


12.2 


10.2 


33 


7 


7.7 


6.4 


10.9 


9.1 


13.7 


11.4 


38 


8 


8.5 


7.1 


12.0 


10.0 


15.1 


12.6 


42 


9 


9.3 


7.8 


13.2 


11.0 


16.5 


13.8 


46 


10 


10.1 


8.4 


14.3 


11.9 


18.0 


15.0 


50 


20 


16.9 


14.1 


24.0 


20.0 


30.2 


25.2 


90 


30 


23.0 


19.2 


32.5 


27.1 


40.7 


33.9 


120 


40 


28.5 


23.8 


40.3 


33.6 


50.9 


42.4 


150 


50 


33.6 


28.0 


47.7 


39.8 


60.0 


50.0 


180 


60 


38.6 


32.2 


54.6 


45.5 


68.7 


57.3 


200 


70 


43.3 


36.1 


61.4 


51.2 


77.3 


64.4 


225 


80 


48.0 


40.0 


67.9 


56.6 


85.2 


71.0 


250 


90 


52.4 


43.7 


73.9 


61.6 


93.1 


77.6 


275 


100 


i 56.7 


47.3 


80.2 


66.8 


100.8 


84.0 


300 


200 


1 95.4 


79.5 


134.6 


112.2 


169.7 


141.4 


550 


300 


129.0 


107.7 


182.9 


152.4 


229.7 


191.4 


750 


400 


160.0 


133.6 


227.0 


189.2 


285.6 


238.0 


880 


500 


190.0 


158.0 


268.0 


223.5 


336.6 


280.5 


980 


600 


216.0 


180.0 


307.0 


256.0 


387.0 


322.8 


1,050 


640 


230.0 


2192 . 


323.0 


269.0 


406.3 


338.6 


1,100 



1 Based on Santa Fe Table 30. 

2 200 second feet by Table 28. 



222 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Table 28. — Maximum Runoff, Dickexs Formula 

D = C\/M^ Runoff expressed in second feet 
The following tabulation is for a 24 hour precipitation of 4 in. rain and for 
topography similar to the farming sections of the Eastern Atlantic States. 
For 6 in. in 24 hours correct the quantities in proportion to C as follows : 

4-in. rainfall 6-in. rainfall 

Flat country C = 200 Flat country C = 300 

Rolhng country C = 250 Rolling country C = 325 

HHly country C = 300 Hilly country C = 350 

For steep stony watersheds and a 6-in. rainfall use the Oklahoma Column 
of Table 30. 



Area in square miles 



Flat countrj- 
C 200 



Rolling country 
C 250 



Hilly country 
C 300 



0.1 =64 acres 


36 


45 


54 


0.2 


60 


75 


90 


0.3 


81 


101 


121 


0.4 


100 


125 


150 


0.5 


119 


149 


180 


0.6 


136 


170 


204 


0.7 


153 


191 


229 


0.8 


169 


211 


253 


0.9 


185 


231 


277 


1.0 


200 


250 


300 


2.0 


334 


417 


501 


3.0 


456 


570 


684 


4.0 


564 


705 


846 


5.0 


668 


835 


1002 


6.0 


764 


955 


1146 


7.0 


860 


1075 


1290 


8.0 


950 


1188 


1426 


9.0 


1038 


1297 


1556 


10.0 


1122 


1402 


1682 


20.0 


1890 


2362 


2834 


30.0 


2560 


3200 


3840 


40.0 


3180 


3975 


4770 


50.0 


3760 


4700 


5640 


60.0 


4310 


5400 , 


6480 


70.0 


4840 


6050 


7260 


80.0 


5360 


6700 


8040 


90.0 


5840 


7300 


8760 


100.0 


6320 


7900 


9480 



For areas under 0.1 square mile, see Table 27 



DRAINAGE 



223 







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224 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



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DRAINAGE 



225 



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15 



226 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Table 31. — New York Central and Hudson River R. R. Culverts 
FOR Small Drainage Areas 



steep, rocky 
ground. Acres 


Flat cultivation, 
long valley. Acres 


Size. Diameter in 
inches 


Equivalent capacity. 
Pipes 


5 


10 


10 




10 


20 


12 




20 


40 


16 




25 


50 


18 


two 16-in. pipes 


30 


60 


20 


two 16-in, pipes 


45 


90 


24 


two 18-in. pipes 


70 


140 


30 


two 24-in. pipes 


110 


220 


36 


two 30-iii. pipes 


150 


300 


42 


two 30-in. pipes 


180 


360 


48 


two 36-in. pipes 


280 


560 


60 





Note. — To be used only in the absence of more reliable information 
particularly existing culverts over the same stream. 

Table 32. — Culvert Design. Iowa State Highway Commission 



Size of culvert opening, ft. 


Maximum acres 


Minimum acres 


2X2 


70 


28 


4X4 


376 


140 


6X6 


1300 


520 


8X8 


2700 


1120 


10 X 10 


5000 


2000 



portioned to the runoff but for small areas the size is determined 
by the convenience of cleaning rather than by the discharge 
capacity. Where sufficient fall can be obtained to make the 
culvert self-cleaning, a 12 in. pipe is feasible under shallow fills 
but where the flow is sluggish, nothing less than a 16 or 18 
in. pipe will serve satisfactorily. Long culverts under deep 
fills should never be smaller than 2 ft. wide and 3 ft. high to 
permit cleaning by hand if necessary. 

The self-cleansing velocity of flow for sand and earth particles 
is about 1 ft. per second; for coarse gravel about 3 ft. per second 
(Ogden's Sewer Design, page 134). A pipe laid on a slope 
that gives a velocity of 5 ft. per second when flowing one quarter 
full should keep clean. This requires a fall of approximately 



DRAINAGE 



227 



2 ft. per hunderd for a 12 in. pipe and is the minimum grade 
'at which the 12 in. size should be used. 

It is probable that a culvert should have the same slope as the 
stream bed. If given a greater slope the outlet end tends to 
clog and if a lesser the inlet end will plug. It is unusual for 
culverts to fill badly except when placed at the foot of a steep hill- 
side where the stream velocity is naturally reduced. At such 
points an extra large structure should be designed with the idea 
of providing sufficient waterway even after the contraction 
caused by this settlement has occurred. Such a culvert should 
be cleaned after each freshet. The use of short paved dips 
in the roadway at such points in place of culverts is not advised 
as they are dangerous and cause accidents unless very gradual. 



^7^777m^ 






.Roac^ Profile 



PorVion a f Road ■■' /'-Low. Wafer Culver t 

designed as spilling Profile 

'Flood L^y<?l 




Qoncre+e Pavement 
and Shoulders, 



557? 




Natural Ground 



Section A-A 
Fig. 100. 



A man not famihar with the road often loses control of his car. 

If, however, too much trouble is experienced in carrying 
large infrequent floods under the road a small culvert can be 
used for the low water flow which does not as a rule carry much 
silt and the flood flow can be carried over the roadbed by paving 
the entire surface with concrete from toe of slope to toe of slope 
and giving the longitudinal road profile a slight dip safe for 
traffic to localize the flooded portion of the road. (Fig. 100). 

More trouble is experienced from culverts becoming filled 
with ice due to alternate freezing and thawing weather. This 
is particularly true of small culverts draining springs. Culverts 
as large as 2 X 2 have frozen solid in this manner and if this 
difficulty is anticipated the size should be regulated accordingly 
or trouble will be experienced during the spring break up. 
The following ingenious expedient has been successfully used 
on roads where the culverts fill with ice and snow during the 



22S lOCATIOX, GBADI^G AND DRAINAGE OF HIGHWAYS 




— -^ ^ n a 




DRAINAGE 229 

winter. A small pipe is suspended inside of the normal culvert. 

In the fall this small pipe is plugged and in the spring just as 

the snow begins to melt the plugs are removed and 

the first water flowing through the small pipe melts 

the ice and snow rapidly for the entire length of the 

culvert so that it is generally completely free to 

handle the main spring runoff. Pj^ j^q2. 

Grade and Elevation of Inverts. — As previously Small pipe in 
stated it is desirable to prevent silting up of the 
culvert due to abrupt changes in the velocity of flow. For 
this reason culverts are normally given the same slope as the 
stream bed. 

The elevation of the invert is always made low enough to drain 
all surface water from the upstream adjacent lands and if the 
elevation of the outlet permits it is desirable to make the culvert 
low enough to act as an outlet for farm underdrains. In hilly 
country underdrainage need not be given much weight but in 
flat country it often controls the elevation of the culvert invert. 

In order to prevent serious ponding and damage to crops in 
flat country, all culverts or bridges on channels of any importance 
should be placed at such an elevation that the top of the waterway 
opening is as low or lower than the surrounding farm land. 
That is, the culvert elevation and shape of opening is designed 
for the hydraulic grade of maximum flood flow. 




$77/W 



rrsr'^' 



Hilly CounhLf. No danger 
\ of serious ponding 



Fig. 103. 

Figure 104 illustrates this point. The waterway areas of two 
culverts A and B are the same in size. However in order to 
get the full capacity of A the water would have to back up and 
overflow the surrounding lands. Culvert B carries the flood 
flow without serious ponding. 

The use of bridge openings similar to A is very common 
practice in both railroad and highway design as it generally 
cheapens the culvert but is undesirable as causing needless 
damage to the abutting properties. 



230 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



Depth of Cushion under Pavement. — A cushion of earth be- 
tween the top of a concrete culvert or pipe and the bottom of the 
pavement is desirable. This is more important where the 
pavement is a rigid type such as brick or concrete than where 
it is a macadam construction. 

The depth of this cushion sometimes controls the culvert 
invert elevation where the topography and road grade makes 
a low invert needlessly expensive or impracticable. 



Hyc!r(yiuU'c Grade A •. 
?hod El9V. A •. 




Flood EIqv. B 

[ 'HL/drcmjIic Grade B 



-Invert ■'' 



'Gqneral Ele\/afion Surrounding Farmland 
Fig 104. 

For rigid pavements the minimum desirable depth of cushion 
is approximately 6 in.; if less than this is used the chances are 
that the pavement will crack over the side walls of the culvert 
unless the pavement base is specially thickened and reinforced 
with steel. For macadam pavements a 6 in. cushion is desira- 
ble but no great damage occurs if the bottom course is laid di- 
rectly on the culvert top. Even with a cushion settlement often 
develops each side of culverts having less than 2 to 3 ft. of cover 
but it can be easily fixed by the maintenance gang. 



Topof Culver f- 



Pavement. 



Ear til Cushion 
between Pavement 
cxnd Culvert 



V/////////// ///////////////////////7ZZ1 
Fig. 105. 

{d) Dead and Live Loads. — Dead loads are readily determined 
but reasonable live loads are a matter of judgment. Many 
of the states limit a vehicle load to 15 tons on improved roads 
without special permission but loads in excess of this occur 
now arid then. The old culverts and bridges on our roads are 
practically without exception too light for modern traffic. 
Permanent culverts should be designed to carry the dead load 
plus a 20 ton vehicle load with 25 per cent, impact. Standard 



DRAINAGE 231 

culverts often seem needlessly strong but small concrete culverts 
are generally backfilled and used during construction before 
they develop their full strength and practical considerations 
require the excess material. A design load of a 20 ton vehicle 
with 30 per cent, impact is desirable for small permanent solid 
floor bridges of 10 ft. to 50 ft. span and this loading is often 
used for even timber bridges in states similar to Wyoming 
where oil development, etc., requires the movement of heavy 
machinery, although usually where timber is used a 10 ton live 
load with 50 per cent, impact is considered good practice and 
for mountain roads 6 tons will usually be acceptable. For long 
span solid floor steel or masonry structures a live load of 150 lb. 
per sq. ft. plus a 20 ton vehicle with 30 per cent, impact is first 
class modern practice. This value is higher than generally used. 
These loadings are safe for military purposes as the following 
statement of Major General W. M. Black, Chief of Engineers 
1917 will show. 

"Our existing ordinance liable to accompany a field army will have 
its heaviest representative in a 12-inch howitzer weighing about 27,000 
lb., 18,600 lb. of which are on the front wheels. The base or distance 
between the front and rear axles is 18 ft., width of track 7 ft. 4 in., width 
of tire 8 inches; width of tire shoes 12 inches. This howitzer is drawn 
by a 75 hp. caterpillar tractor weighing 25,000 lb. Comparison with 
the largest present day commercial trucks shows that a road or bridge 
substantial enough for such will suffice for the ordinance load." 

The safe load for steel I beams, timber, reinforced concrete 
beams and slabs are given in the third book of this series. 

(e) Length of Structure. — Culverts are made long enough 
to accommodate the normal road section. There is nothing 
more unsightly or dangerous than the narrowing of the normal 
section at a culvert. First class design widens the section at 
culvert locations and even with minimum head room uses a 
clear roadway width between parapets of not less than 20 ft. 
on single track roads and not less than 26 ft. on double track 
roads. Short span permanent bridges up to about 25 ft. span 
on high type road improvements may well have a clear width of 
not less than 22 ft. between parapets. Above 25 ft. spans the 
roadway width depends largely on the location of the structure 
and probable traffic but for most main roads a 20 ft. clear roadway 
is satisfactory for permanent structures and a 16 ft. roadway for 



232 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 




DRAINAGE 233 

temporary timber structures. Figures 114 to 128 illustrate cur- 
rent practice. 

(/) Economical Type of Structure. — The selection of type 
for any particular structure depends on the foundation soil, 
the requirements of topography and the relative economy of 
the different designs suitable for the location. 

On dry firm foundations any type is satisfactory. On wet 
or moderately soft soils tile or concrete pipe culverts should be 
cradled in concrete; the concrete box type of culvert is probably 
more desirable for these conditions as the load is transmitted 
vertically in well defined directions. On quicksand or muck 
foundations the flat slab vertical side wall box type with timber 
sub foundation or pile and grillage is in general favor. Con- 
sidering the usual foundation conditions the author prefers the 
flat slab or girder type of small span bridge in most cases unless 
there is a noticeable economy in some other form. 

For small drainage areas some form of pipe culvert is generally 
used which will be discussed later in more detail. 

From 2 ft. to 5 ft. spans the box culvert type is popular. 

From 5 ft. to 20 ft. spans the slab, stringer or parapet girder 
form of construction is reasonable except under deep fills where 
the semicircular arch is better practice; from 20 ft. to 50 ft. 
spans pony truss or parapet girder types are available for most 
conditions or arches where the foundation is suitable. Pony 
trusses are desirable up to about 80 ft. span and beyond that 
the through Truss type. 

The following list illustrates the practice of the Iowa Highway 
Commission. 

1. Box culverts and slab bridges 2 to 20 ft. span. Not economical over 
20 ft. span. 

2. Reinforced concrete arches 8 to 100 ft. span. Foundation must be 
excellent. 

3. Pony truss steel bridges with solid concrete floor 30 to 80 ft. spans. 

4. Reinforced concrete girders 20 to 50 ft. span. Very economical 
but require careful design and construction. Not economical over 50 ft. 
span. 

In the matter of type the author desires to emphasize the 
desirability of simple design particularly for small structures. 
Mass concrete for sides and bottoms is preferable to thin rein- 
forced sections (see New York Standards, page 246). It may 
not be as scientific or theoretically as cheap but better results 



234 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



/^ "^ 


^iL^M i 


iMIftn 


"^^8 


• "^ijp^^^ ^'"' 


SHIb^.' 


— ' 


^:;f :^ 




WM 




«< X 'f^^^^Kk 'v^^HH^^^^ ^^^^^^Hl 


^H 




^^^^^^^^^^BB ^39' '^^^^fl^- '''< *^ 


Hh &.. m- V 




^^^^■;; ^'^^'^^f^^^^^s^^.^ii^si 


^OtUtm " '^''^HlEkjMss. 




m^^^^^^^^u 


' '^^^^ 


te^Tl' -^"^ --5^. 


^■^- ■----*«'- 


i 







Fig. 107. — Simple concrete box culvert with straight high parapets (Town road 

construction) . 




Fig. 108. — Double box culvert (town road construction). 



DRAINAGE 



235 




Fig. 109. — A crude log stringer bridge. Pioneer road work. 




Fig. 110. — Usual type of timber stringer bridge (unimportant roads). 



236 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



.^ 




BHHI l^^^^^^^^^^^^^^^w^i ^-v." - 


i j^\»^mM|^jji^^^^^BB 





Fig. 111. — Parapet girder bridge (concrete). High class road. Span 25 ft. 
Width of roading 22 ft. Approximate cost (1920) $5000. Actual cost (1914) 

$2300. 




Fig. 112. — Arch type on rock foundation. This is a \-iew of tlie bridge the 
plans of which are shown in detail in Fig. 12S. Total span 50 ft. Approx. cost 
(1920) .$5000. Actual cost (1915) $2500. 



DRAINAGE 



237 




OS 

o 

Q 



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00 

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Pi 



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238 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

are obtained with the usual inspectors. Road commissioners 
often do not understand the object of the reinforcement and either 
leave it out altogether or get it in the wrong place. For large 
structures where a competent inspector can be employed this 
objection does not hold but even for such structure mass concrete 
for abutments, retaining wall, etc., is to be preferred. Mass 
concrete 1:3:6, mixed with embedded boulders is satisfactory. 
Reinforced culvert concrete is usually made 1:2:4 mix. 

Pipe Culverts. — The pipe culverts in common use are as follows 
(see Figs. 115 to 118, pages 241 to 244, for typical pipe): 

Culvert Designs 

Corrugated metal Semi-permanent construction 

Vitrified tile Semi-permanent construction 

Reinforced concrete pipe Semi-permanent construction 

Vitrified tile incased in concrete Permanent construction 

Reinforced concrete pipe cradled in concrete. Permanent construction 

Cast iron pipe Permanent construction 

These types of culvert are suitable on firm foundations and 
generally economical for small drainage areas. The relative 
cost will fluctuate for each contract which makes it impossible 
to generalize as to the economy of selection. 

Box Culverts. — The two general types favored are the plain 
mass concrete bottom and side wall with reinforced cover slab 
and the lighter box reinforced on all sides (see Figs. 120 and 121). 

Relative Economy of Culverts. — Comparative estimates of 
cost must be made for each contract but to give a general idea 
of the method of economical selection the following table is 
inserted for 1920 cost conditions prevailing in western New York. 

The semi-permanent types should not be used on high class 
improvements except for driveway culverts. 

Comparative estimates similar to Table 33 furnish a rational 
basis for judgment provided only the permanent types are 
compared and provided the comparison is made for each contract 
considering the special conditions prevailing due to location, 
market quotations on materials and local materials available. 

For conditions similar to Table 33, Western New York, 1920 
permanent pipe culverts are not economical over 18 in. in diameter. 
For drainage areas requiring a culvert waterway area of over 
2 sq. ft. the box type is preferable. Of the box types the simple 
mass concrete structures are in the author's opinion more satis- 



DRAINAGE 



239 



factory, considering construction difficulties than the thin wall 
reinforced type although they cost somewhat more than the thin 
sidewall type. This, however, is a matter of personal judgment. 



Table 33. — Approximate Relative Cost of Pipe and Box Culverts 
30 Ft. Long Including Headwalls (Exclusr^e of Excavation) 



Size Area 

culvert waterwa3 
pipe, in. sq. ft. 



Style of construction 



Corru- 
gated 
metal 



Vitrified 
tile 



Vitrified 

tile 

incased in 

concrete 



Reinforced 

concrete 

pipe 



Reinforced 

concrete 

pipe 

cradled in 
concrete 



Cast 
iron 
pipe 



12 


0.78 


$60 


$50 


$65 


$75 


$90 


$100 


14 


1.07 


70 


60 


75 


80 


95 


130 


18 


1.76 


90 


80 


110 


100 


130 


170 


24 


3.14 


120 


120 


160 


135 


175 


260 


30 


4.88 


140 


180 


230 


180 


230 




36 


7.05 


170 


260 


310 


240 


290 




42 


9.60 


200 






300 


360 




48 


12.52 


230 










■ 





Area 
waterway, 
sq. ft. 


Style of construction, concrete boxes 


Size culvert 
opening span-height. 


Mass concrete bottom 
and sides (Fig. 120) 


Thin Reinforced Sides 
and bottom (Fig. 121) 




Total 
cost 


Cost per 

sq. ft. 
waterway 


Total 
cost 


Cost per 

sq. ft. 
waterway 


2 X 1.5 

2X2 

3X2 

3X3 

3X4 

4X2 

4X3 

4X4 

5X3 

5X4 

5X5 


3 

4 

6 

9 

12 

8 

12 

16 

15 

20 

25 


$160 
190 
210 
260 
300 
250 
300 
340 
350 
400 
450 


$57 
50 
37 
30 
26 
31 
25 
21 
23 
20 
18 


$150 
200 
230 
300 
350 


$35 
22 
30 
20 
17 



Examples of Current Practice in Pipe & Box Culverts. — The 
following cuts illustrate typical practice in small culvert 
design. 



240 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



j^ g 










DRAINAGE 



241 




16 



242 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



\i----4 Max -•->( 



Min'imurr? n 
Zushion 6 



'Cl.dfCJJverTj 



" " ^'/ 
12, 1 Bar 18. 



Half Plan 

\_^_^^_3>!ngle Track Road Mlnirnum [I 
""'Dbubh '} >i '> Is'" 



^mm-i^smM m 




I 



Minimum 



Invert Grade '^% 



Half Section 
on Cu Ivert Center Line 




WeU Tamped Backfill 

CHafural Mai^rial) /ifLeasf&'l p"m' l:3:GConcrsfe 



Jacket" 



Boffom 
Pavcmen: 




Plank if 
necessary 



FIRM SOI LS-//^/-^/^ CLAYORLOAM mnctari e cnii «i 

Qnavd or Coarse Sana, or in firm soils unsiABLt iUiL;j 

provided there is a where cushion^^ 

mini mum cushion of at is less than I? 
least 12" 

SECTION A-A-Showing Treatment in Different Soils- 
FiG. 116. — Typical vitrified pipe culverts. 



Approximate Weights, Dimensions, Etc. of Standard Sewer Pipe 



Calibre, in. 


Price 
per foot 


Weight, per 
foot, lbs. 


•Depth of 
socket, in. 


Annular 
space, in. 


Thickness, 
in. 


12 


$1.35 


45 


2M 


y2 


1 


15 


1.80 


60 


2K 


. Vi 


IM 


18 


2.50 


85 


2M 


K 


Vi 


20 


3.00 


100 


3 


>^ 


1% 


22 


4.00 


130 


3 


M 


1% 


24 


4.50 


140 


3M 


M 


m 


Double Strength Pipe 


X'alibre, in. 


Price 
per foot 


Weight per 
foot, lbs. 


Depth of 
socket, in. 


Annular 
Bpace, in. 


Thickness, 
in. 


15 


$1.80 


75 


2M 


Yi 


IM 


18 


2.50 


118 


2^i 


V2 


13^ 


20 


3.00 


138 


3 


H 


m 


22 


4.00 


157 


3 


y^ 


1% 


24 


4.50 

1 . .. . 


190 


3M 


V2 


2 



DRAINAGE 



243 




«r- - 



Singh Track Road Minimum // 



Doubh » 



Zushion 6- 



■Pavemeri] 






Minimum ii Ufi>Wr(im^)k\^''i)% ^ '' ' ^fd 



4 



Minimum\ \ Invert GradA '^% 

Ho If Section U/*^ 

on Culvert Center Line ^ 




Wq}} Tawped Backfill 
rHafuralMafer/al) AfLeasf^'l 2%jn., ''■^i^Slf'^^ 



Bothni 
Pavemen. 




Plank if 
necessary 



?\RVi sows-Hard Pan CLAYOR LOAM iiNSTABLE SOILS 

Gravel or Coarse Sana, orin firm soils UNi>TABLE :>yiL;> 

provided there is a where cushion^ 

minimum cushion of at is less than 12 
least 12" 

SECTION A-A- Showing Treatment in Different Soils- 



W^^^W/r'^^^^W^. 



^ 






l ^^^^^^4 :fe^gzS^ 



-^ 



TABLZ OF DIMENSIONS AND 
REINFORCEf^ENT FOR PIPE 



Table of Dimensions 



' D 

Inches 


L-Mox. 
FGe+ 


T 
Inches 


B-Min. 
Inches 


E 
Inches 


12 


4 


Z 


ZVz 


272 


15 


4 


2, 


2 /a 


2'k 


18 


4 


2% 


I 


3 


24 


4 


i 


3 


3/2 


E-Pfective Areaof Circumferal 
Refnfbrcement 
Pe'- Foot Length of Pipe 


\1 


0.058 Sq. Inches 1 


15 


0.056 V T. 


1 


18 


0.080 " r> 


24 


0.126 f. u 


Approximate Weight Per Linear Foot 


of Pipe 1 


12 


90 lbs 


15 


110 w 


18 


170 r, 


24 


250 '7 



Fig. 117. — Typical reinforced concrete pipe culverts. 



244 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



P I a rt 




I ^v 2,NofLessfhan. 

S'-W 




Long^i+udinal Sec+i'on. 
Fig. 118. — Cast iron pipe culvert. Xew York State standard. 




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fe "5 5 §: g 



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DRAINAGE 



245 




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246 LOCATION, GRADING AXD DRAIXAGE OF HIGHWAYS 




'^'^ ^f^..., ty 






-ir- 



Cross Se;",:- *;r 
CoUapsibie Forms. 




. J. , c ■ (Mil I^^2and2'x2 End Wall. 

Longitudinal Section. Q/fvern tobeBviltwifh 
EndYfy/b.) 




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a 

c 


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' - Z' 


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Table of Dimensions . 



V-3»«/<a?=riT?-'-i'' 



13 

:'3' 



^&^ 






U/5'>j Longitudinal Section. 

For effect of depth of fill on tliickiiess 



•Dowels 0.2S'^ 
Net Area ^ ^-, 



Parr 
Cn»5 Section. 



of cover slab see Voliime 3. 
Fig. 120. — Xew York State small box culverts. 



DRAINAGE 



247 



Longitvdi'nal Rods 20'fo27ZtoC. 




l^... £■'... )i 'Concrete 
Asiomption for Live Load. 



. .„5 k morv thanlB'Cfrf' g *p 

W^SpanslessfhanSft ^ 

Comers notfess than 6' 
LonaJ9xls Same SizeeaS/des 
andB^tom^ 



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n forSidesand 

! Bottom otid' 

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Cross Section of CuWerh 



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Fig. 121. 



248 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

SMALL SPAN BRIDGES 

Economic small span bridge design is susceptible to con- 
siderable variation of tj^pe. 

Size of waterway, width of roadway; live and dead loading 
have been outlined. 

The superstructure up to a span of 25 ft. is generally the 
slab or reinforced concrete parapet girder design on high class 
roads and the timber stringer on king post truss design on pioneer 
roads. Figures 122 to 128 illustrate current practice. George 
C. Wright; bridge designer for Monroe County, New York, 
states that for conditions prevailing in this country the parapet 
girder type is more economical than the slab design for spans 
greater than 10 to 15 ft. The parapet girder type should not how- 
ever be used unless the construction inspection is intelligent and 
rigid. 

Foundation Soils. — The foundation design and to a certain 
extent the type of superstructure is affected by the soil. Most 
ordinary soils afford satisfactory foundations for small span 
bridges but piles must be used for muck or quicksand and are 
advisable if much scour is anticipated which can not be pre- 
vented by rip rap protection. Pile foundations are required for 
all large structures where rock foundations are not available and 
are desirable for any concrete structure over 30 ft. span. 

Where much ice occurs piers in small streams should be 
avoided. They can be used to advantage to reduce cost, how- 
ever, if there is no danger of ice or debris jams particularly if 
the flow is sluggish and in the latter case for wide shallow streams 
the trestle design is appropriate. 

The safe foundation load on various soils recommended by 
'^Baker's Foundations'' are as foUows: 

Rock (poor) 5 tons per sq. ft. 

Rock (solid and first quality) 25 tons per sq. ft. 

Dry clay 4 tons per sq. ft. 

Medium dry clay 2 tons per sq. ft. 

Soft clay. 1 ton per sq. ft. 

Cemented gravel 8 tons per sq. ft. 

Compact sand 4 tons per sq. ft. 

Clean dry sand 2 tons per sq. ft. 

Quicksand and alluvial soil K ton per sq. ft. 

Pile Loading. — Where piles are used for types of construction 
where slight settlement is not objectionable (slab, girder or truss 



DRAINAGE 



249 



UOI4.099 



^Jr ^ ^ 




•4^ <r 



250 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 





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252 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



















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DRAINAGE 



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lii-4. — 



DRAINAGE 



255 




I '---/fods 0.25'"'NetArea. 
\ Spaced IZ"C.toC. 

W\{Spans5'fo25:) 
Plan. 



NOTB 

All rods to have a deformed 
cross-section. All rib metal to be 
of medium steel. 

2d class concrete in all slabs 
and parapets. 3d class concrete 
in wings invert and abutments. 
Wing walls on the outlet end of 
all square culverts with concrete 
floors to be built parallel to the 
center Une of the culvert. Round 
all exposed edges to z} inch 
radius. 



( Heights 5'to is!) 







.■Rods in Slab to be Extent 
\ ded 24 Diams. beyond 
\ Neat Lines of \ 
Abutment 



DoyvelsO.25 
IZ'Xtrs. 
Pile Foundations to be 
Used in lightand Shift- 
ing Soils. Pave when 
Ordered byDiv.Engineer. 




Elevation. 



BoltomWidfhof'the ' ' '~^-'" 
Abutments not less than 
4 of Total Height from Bottom 
of Abutment to Top of Slab, v 

Section on Center Une 



For Typical 
Section "F" 

Where culvert covers 
become a part of con- 
crete base for brick 
pavement, transverse 
reinforcement should be 
extended 12" beyond 
back of abutment into 
concrete base^ 



IS^fprAS'SkewX 

lOtvrmrlS'A 

\ 



Rods in 3 la btv be 
Extended 24 Diams. 
beyond Neat Lines 
of the Abutments. 




Rods 0.25' 
NetAreO; , 
Spaced IZ 
C.toC^ 



Dimensions of slabs on page 256. 
Fig. 125. — New York State slab bridges. 



256 LOCATION y GRADING AND DRAINAGE OF HIGHWAYS 



Span 


Thickness of 

Skb» 


Net Area 

of 

Rods 


Rod 

Spacing 
C-C 


Length 

of 
Dowels 


5 


8' 


o.25sq." 


4V 


12' 


6 


9' 


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7 


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sr 


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For Spans 5' to 19' W = 18' For Clear Height 10' or less 
" "' 5' to 19' W = 24' " '' " 11' to 15' 

" •• 20' to 25' W = 24' " " " 15' or less 

For Gear Height 7' or less E = 3'- o' 
8' to 10' E = 4'- o' 
above 10' E = 5'- o' 

* Note. — The thickness of slab given is for shallow fills. Foi 
the efifect of deep fills see Volume III. 



Fig. 125. — {Continued), 



DRAINAGE 



257 



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258 LOCATION, GRADI^'G AXD DRAINAGE OF HIGHWAYS 




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DRAINAGE 



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mill iri ill 




260 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 



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262 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

types) a design loading of from 10 to 15 tons per pile for sound 
well driven piles is conservative practice. 

The safe load on a pile as actually driven during construction 
is given in. Volume IT. 

Scofur. — Scour is produced in di^erent soils at approxiniiitely 
ihe following velocities : 

Sand 2 to 3 ft. per second 

Loam. 2 to 3}4 ft. per second 

Finr; gravel 5 to 6 ft. per second 

Rip rap reduces scour and will usually protect the banks from 
scour up to a velocity of about 12 ft. per second if well placed 
and made of large stone of J^ cu. ft. or larger volume. 

If the natural stream velocity is not greater than 10 ft. per 
second the span is usually regulated so that the velocity under 
the bridge will not exceed 10 ft. per second. 

2. Lotigitudinal Drainage. — Longitudinal drainage covers the 
normal road section ditch, special creek channels^ the protection 
ci ditehes froDi aeoor ou steep grades, the use of storm water 
sew&s on long grades, where it is not po^ible to get rid of the 
surface water by diversion from the road,, and driveway culverts. 

CarEjing Capacity erf Ditches. — It is desirable to use as shallow 
and smaQ a road ditch as possible both on the score of safety 
and economy of grading (see Sections page 157). All ditches 
will clog more or less in the winter with snow and ice so that the 
sue of the ordinary road ditch is more a matter of judgment 
based on experience than that it is of figures. Intercepting 
ditches carrying the runoff from considerable areas should be 
figured using runoffs similar to culvert design methods. 

Creek channels and intercepting ditch capacities can be 
£z;^r.i. C-- : : s diagrams of Kutteris ::rzi;^:e ising a value 
ci n = 0.035 lurnish a quick easy method of approximately the 
required size. Volume m takes up the design methods of 
determining the volume of flow in small streams. 

In order to give a fairly definite idea of the limitarions of the 
nse of the shallow and medium road ditches shown in Fig. 67 
and reproduced below the following conditions are outlined. 
As a rule the capacity of the roadway ditch is taxed by short 
sharp summer showers. As previously discussed it is desirable 
to use special intercepting ditches if much water flows from 
tiie adjacent lands onto the road right of way. Assuming that 



DRAINAGE 



263 



this has been done the road ditch proper only carries the water 
from one-half the road section plus the area of back cut slopes 
or small areas of farm land. The runoff from the pavement 
proper is about 80 to 90 per cent, of the rainfall for showers of 
say 10 minutes duration. The runoff from the shoulders and 
backslopes is perhaps 60 per cent, under favorable conditions. 
We can assume an average runoff of about 75 to 80 per cent, of 
the rainfall for the area of one-half the total right of way width. 
This means as a rule that the shallow ditch should not be used 
for more than 400 ft. from a summit or below a ditch relief 
culvert on flat grades or more than 800 ft. on moderate grades. 
Current practice recognizes this general principle by the use of 
deeper and larger ditches in flat country than in rolling country. 
The medium ditch will serve satisfactorily for at least 2000 ft. 
from summits provided it does not carry side land runoff. 



J t SH/ILLOWRO/IP DITCH 



,js Water Levef; 




Cro <yvn Grade j, | fsj 

^-8-0- 



-C MEDIUM ROAD DITCH 

i^ Wcn^-er Leve!- ,„" 



4 CepthofWaf-er 




[< 14-0--- ^ofiVcffer 



Fig, 129. 



To give a rough idea of the carrying capacity of ditches 
a condensed table is given for a few ordinary cases. 

Table 34. — Table Approximate Carrying Capacities and Velocities 
OF Flow Ordinary Road Ditches Grassed Over 





Shallow ditch, 
Figure No. 129 


Medium ditch. 
Figure No. 129 


Grade of 

road ditch, 

per cent. 


Velocity, 
ft. 


Capacity, 
sec. ft. 


Depth water, 12 in. Depth water, 6 in. 




Velocity, ft. 


Capacity, 
sec. ft. 


Velocity, ft. 


Capacity, 
sec. ft. 


1.0 


0.7 


0.4 


2.0 


4.0 


1.1 


0.5 


2.0 


1.1 


0.7 


3.0 


6.0 


1.7 


0.8 


3.0 


1.3 


0.8 


3.6 


7.2 


2.0 


1.0 


4.0 


1.5 


0.9 


4.2 


8.4 


2.3 


1.2 


5.0 


1.7 


1.0 


4.8 


9.6 


2.6 


1.3 


6.0 


1.8 


1.1 


5.3 


10.6 


2.8 


1.4 


7.0 


2.0 


1.2 


5.6 


11.2 


3.1 


1.5 


8.0 


2.2 


1.3 


6.0 


12.0 


3.4 


1.7 


9.0 


2.3 


1.4 


6.5 


13.0 


3.6 


1.8 


10.0 


2.5 


1.5 


7.0 


14.0 


3.8 


1.9 



264 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

Protection of Ditches from Scour. — The rate of grade at 
which ditch protection from scour is advisable depends on the 
soil and velocity of flow ; the velocity of flow depends on the shape 
of ditch and volume of water. 

Soils scour at approximately the following velocities: 

Sand 2 to 3 ft. per second 

Loam 2 to 3>^ ft. per second 

Firm gravel 5 to 6 ft. per second 

Foregoing Table 34 is inserted to show in a general way 
the effect of shape of ditch and depth of flow on velocity and 
indicates that ditch protection must be provided at lower rates 
of grade for a large flow than for a small flow. This agrees 
with current practice which favors the use of cobble or cement 
gutter at approximately the following rates of grade. 

Current Practice in Ditch Protection. — Where the volume 
of flow is less than 1.0 sec. ft. ditch protection is not needed 
on hills less than 7 per cent, grades. Where the volume of flow 




Pitch Prd'tecfion. Usual Practice 

-' -; — -----y 

Ditch) Protection. Recommendeci 



Easy Grade 



•f 1 



Profile 
Fig. 130. 



Culvsrt ' 



exceeds this amount ditch protection is advisable on sandy or 
loam soils on grades steeper than 3 per cent, and in firm gravel 
on grades of 5 per cent, or greater. This means that as a rule 
on steep grades some kind of gutter is desirable for ditches 
more than 200 to 300 ft. from a summit or below a ditch relief 
culvert. It is practically impossible to carry a large volume 
of water down a steep grade so that every effort should be made 
to divert the flow above the grade or remove it from the surface 
by ditch relief culverts or storm sewers. 

Where ditch protection is -used it is good practice to carry 
it for at least 200 ft. along the road after the foot of the steep 
grade is reached and preferably to the first culvert below the 
grade in question as scour often occurs through stopping the 
protection too closely to the bottom of the steep grade. 



DRAINAGE 



265 



Cobble gutter with cement joints on grades over 6 per cent, 
and sand or gravel joint filler on grades less than 6 per cent, 
where the volume of flow is not large is probably the best design 
as it tends to retard the velocity of flow. 

The smooth concrete ditch lining is not usually satisfactory 
on steep grades but is allowable if the cobble gutter is not 
available. 



^hov/dt 




Sand 
Cushion 



( Sand-Cushion not Required in Sandy Soil 
Size of Stone 5-9.") 

Cobble Gutter. 




3'0"-^->l 



Third Class Concrete 
Ditch Lining. 




i (Usual 8^/bwJi 



i<v- 



ConcreteorSand Foundation; Grouted 

or Sartd Joints. 
Brick Gutter. 




•k-— 3'^'— >1 



No.4 Crushed Stone 
Ditch Protection. 

Fig. 131. 



Storm Sewers on Hills.^ — Where it is impossible to divert 
the water from the surface on long hills a storm sewer system 
is sometimes used. 

Catch basin inlets are constructed at intervals of 200 to 400 ft. 

The size of pipe are figured for probable runoff in the same 
manner as for culverts. Table 35 given below gives a rough 
approximation of the carrying capacity of different sized pipes 
laid on different grades. 



266 LOCATIOX, GRADING AND DRAINAGE OF HIGHWAYS 

Table S5^ — Approximate Flow Capacity in Cubic Feet per Secoxd 

Value of N = 0.013 



Grade, 
per cent. 



Capacity of flow of different sized pipe 



12 in. 



15 in. 



18 in. 



20 in. 



24 in. 



36 in. 



^ Computed from diagram Ogden's Sewer Design. 



0.5 


2A 


4.4 


7.5 


9.5 


16.0 


42.0 


1.0 


. 3.3 


6.3 


10.5 


14.0 


23.0 


60.0 


1.5 


4.2 


7.6 


13.0 


17.0 


27.0 


75.0 


2.0 


4.8 


8.8 


15.0 


19.0 


31.0 


86.0 


3.0 


i 5.8 


11.0 


18.0 


24.0 


39.0 


105.0 


4.0 


! 6.5 


13.0 


22.0 


27.0 


46.0 


122.0 


5.0 


7.3 


14.0 


24.0 


30.0 


51.0 


137.0 


6.0 


' 8.1 


15.0 


26.0 


33.0 


56.0 


150 . 


7.0 


8.8 


16.0 


27.0 


35.0 


60.0 


162.0 


8.0 


9.5 


17.0 


28. 


38.0 


65.0 


173.0 



Figures 132 and 133 give tjiDical catch basin and simple man- 
hole designs for such a sewer. 




Section. 
Wrought Iron. 
Fig. 132. 



Standard 
dizrtj'ng-' 



3'Diam. 
CircuhrOpeninq-' 

Manhole 




' m\ Standard 
Onxting 



LeaohirL2 Basin. 



Fig. 133. 



Driveway Culverts. — Culverts under drives cause more 
drainage troubles than any other feature as they are usuaU}' 
constructed by the property owner instead of being included 
in the road contract. 

It is an amusing fact that private farm bridges over streams 
or road ditches are notoriously small. Each owner seems to 



DRAINAGE 267 

think that water will get under his drive in a small cheap struc- 
ture and the same man who says that a road structure is too 
small will build a bridge or driveway sluice just below this 
structure that he has been kicking about and make it from 3^o 
to 3^ as large as the main drainage structure unless he is pre- 
vented by law which is enforced by highway officials. 

The size of the structures should be fixed on the road plan 
and designed from the same standpoint as a culvert or bridge. 

Cheaper types of structure are suitable as they can be readily 
replaced without tearing up the pavement. 

Corrugated metal pipe, vitrified tile or reinforced concrete 
tile are suitable but no matter how little water is carried the 
size of driveway culvert should not be less than a 12 in. pipe 
on account of maintenance difficulties. These culverts are 
properly placed in the ditch line at normal ditch grade and 
as a rule 12 ft. length is about the minimum that will be at all 
satisfactory. 

Underdrainage. — The purpose of underdrains on hard sur- 
faced roads is to intercept the ground water before it reaches 
and softens the sub-grade. On a sidehill road the drain is usually 






.§ 




Macadam ^3 yMm^ 



■^ ^M ^'^ j^Direction 

^ ^ Kif_i_ of Seepage 



"I! Position No.Z Position No./ 

Fig. 134. 



placed under the ditch on the uphill side (see Fig. 134, position 
No. 1) where the greatest depth can be obtained with the last 
excavation and where the water is caught as it flows out of the 
hill. 

Some engineers place the drain in position No. 2 (Fig. 134) 
but this requires more excavation for the same depth and for 
side seepage is not as effective. The usual depth for drains 
is 3 ft. to 4 ft. below the surface. 

Where the road is on a descending grade, the water will flow 
out of the hill directly under the stone and the drain is placed 
as in Fig. 135, position 1, or two drains are built in position 
No. 2 . Position 1 is the usual practice, being cheaper and more 
effective. 



268 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

The argument for the two side drains is, that in case the throat 
becomes clogged, a side drain can be taken up without disturb- 
ing the macadam. This rarely occurs in a center drain, as it is 
better protected than those in position 2 and in case the center 
drain does clog, side drains can be constructed at any time. 




±IG. 



There are two kinds of dradn in general use, Fig. 136 : 
No. 1 is built entirely of stone with an open throat roughly 
laid as shown; it is satisfactory in a water-bearing strata of 
gravelly loam of clay, but does not work so well iu quicksand, 
which is liable to fill it up. It is generally cheaper, however, 
than No. 2. 

No. 2 is built of porous farm tile or virrif ^i tile of a sii:::^ le 
size (usually 3 in. to 6 in.) with open joints, wrapped with a 
double or triple layer of burlap; the pipe is surrounded and cov- 
ered with clean gravel or ^1 in. crushed stone to a depth of 6 in., 
the remaining depth of the trench being filled with large stone. 
If this drain has a good fall and the outlet is kept free, it will 
rarely dog even in bad quicksand. 



&.7: 






~--50f 



Fig :?^^ 

The following method has been successfully used to pre- 
vent the outlet from clt^ging; after being brought out from 

under the macadam, the drain is continued under and across 
the ditch line, then keeping outside the ditch line, and using 
a slightly smaller gradient than that of the oi)en ditch, the tile 
is continued down the hfll until it reaches a point eight or nine 
inches above the ditch grade. Here it is turned into the open 
ditch through a small concrete head- wall and what little material 



DRAINAGE 269 

it tends to deposit is washed down the ditch by the suaf ace water 
(see Fig. 137). The lowest rate of grade advisable for under- 
drains is 3 in. per 100 ft. 

Summary of Chapter. — The present bridge situation demands 
attention as even in the richer states it is lagging behind the 
improvement of the roads. The separation of bridge and 
highway funds and the lack of central control often results 
in the ridiculous situation of a modern road limited in use by 
antiquated bridges. 




.51 



-nzzzzzzzzzzz 



Fig. 137. 



Road pavements can be strengthened from year to year by 
additions in thickness and the construction of better surfaces 
on top of existing improvements but structures must be rebuilt 
entire to increase their strength and for this reason more fore- 
sight in regard to future traffic must be exercised in their design. 
A liberal allowance for increased loads is desirable. Liberality 
in size of waterway for culverts is also good policy as it adds 



270 LOCATIOX, GRADIXG AND DRAIXAGE OF HIGHWAYS 

only slightly to the cost and materially decreases the difficulties 
of maintenance. 

The design of drainage must be complete and reasonable 
and it the existing scheme is not feasible it should be changed 
regardless of law-suits as whenever an improvement is made 
it is always cheaper to correct mistakes at that time than it 
will be at a later date as every year's use fix the channels more 
firmly. 

The selection of type ofi'ers the greatest chance for reasonable 
economy in culvert and bridge design. 

CONCLUSION OF VOLUME I 

The discussion of location, grades, ahgnment, section and 
drainage in this volume covers the permanent elements of high- 
way construction. These parts of the design deserve more 
hberahty and foresight in their treatment than the design of the 
pavement surfacing and other minor features of a complete road 
plan. 

Volume II considers the temporary elements of construction 
namely the economical selection and design of pavements; 
methods and cost of maintenance and the problems met in the 
reconstruction of worn out pavements. The reasons for making 
a separate volume of pavement design are that road surfacings 
are a specialized subject in themselves; the problem is approached 
from a somewhat different angle than used in this volume and 
practice in pavement construction is changing so rapidly that 
frequent revisions will be necessary' to keep abreast of approved 
practice. We beUeve by making "" pavements" a separate vol- 
ume which will by necessaiy revisions be kept up to date that 
we will give our readers better continuous service with less cost 
to them and to ourselves than if we had combined Volumes I 
and II into one book. 

This book (Volume I) covers comparatively stable practice. 
Volume n is well along in preparation and wiO be on the market 
in a short time. 



APPENDIX A. HIGHWAY BONDS* 

Reprinted from the Highway Green Book by permission of the American 

Automobile Association 

Before a community invests its money in improved roads it is important 
that plans be made for the ultimate development of a complete system fully 
adequate to serve its needs most economically. The making of such plans 
and the selection of the particular road or roads to be improved should be 
based on sound business principles. Careful consideration should be given 
to the traffic area which the contemplated improvements are to serve; the 
present and probable future traffic in ton-miles per annum; the estimated 
cost of hauling per ton-mile at present and what it probably will be reduced 
by the improvement; the roads which should be improved first; the approxi- 
mate cost of the improvement as borne out by the surveys and estimates 
made by a competent highway engineer; the probable effects of the improve- 
ment on farm values, school consohdation and attendance, community 
betterment and rural delivery of the mails; whether the work can be carried 
on by direct taxation or whether it is desirable to resort to credit; and if 
borrowing is necessary, the best and most economical method of financing. 

As a high standard of pubHc credit is an asset of great value, every com- 
munity should conduct pubHc business upon sound financial principles. 
Bond issues ought to be resorted to only when they cannot be avoided. If 
a county, township or district is able to levy a sufficient tax to improve all 
of the roads required in a reasonable length of time without imposing too 
great a burden on the taxpayers, it should by all means adopt this course. 
It is also axiomatic that maintenance charges for roads and other current 
expenses should always be met from the proceeds of an annual tax levy. 

Comprehensive study of the community's road problems should make 
possible a "\vise decision as to the character and extent of the needed improve- 
ment. If the people deem it advisable to issue bonds and distribute the 
burden over a period of years, then they should determine with careful 
forethought what kind of bonds should be issued, whether long or short term, 
whether sinking-fund or serial bonds, and what taxes should be imposed to 
extinguish the debt. 

The life or term of a bond issue should be determined not only by the 
character of the improvement to be financed, but also by the ability of the 
county, township or district to dispose of the debt as quickly as possible 
without imposing too great a burden upon the taxpayers. The indebtedness 
should be hquidated at a rate at least equivalent to the depreciation of the 
improvements thus financed. The payments should be so distributed over a 
period of years as to avoid the two extremes of excessive or confiscatory levies 
on the one hand to pay off the debt too quickly and the extension on the 

^ Revised by The National City Companj^, New York. 

271 



272 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

other hand of the debt beyond the life of the utihty, in order to obtain a 
low annual tax rate. Sudden and rapid changes of tax rates are to be 
avoided. 

Recognizing the soundness of the principle of hmiting the term of such 
bonds to the life of the improvement. New Jersey and Delaware have expressly 
imposed such Hmitations by statute. In some other States the maximum 
term of public road bonds has been hmited to 15 years, even though the 
roads constructed are the most permanent and durable that is possible to 
build. 



15.000 




9.000 



1400 



Fig. 1. — ^Little advantage is gained through bonds running more than 25 years. 

The New Jersey law may, perhaps, be cited as a model illustration of the 
principle. This law limits the term of pubhc road bonds as follows: For 
stone, concrete and iron bridges, 30 years; for roads and streets built of 
concrete 6 in. thick or of block of any material or sheet asphalt laid on con- 
crete foundation, 20 years; for bituminous concrete construction, 15 years; 
for waterbound macadam, penetration method, 10 years; and for gravel, 5 
years. 

Many road bonds are issued for terms of 30 years and over to obtain a 
low annual charge for interest and principal. Very httle advantage, as is 
shown graphically in Fig. 1, is to be gained by fixing the term of the bond 
longer than 25 or 30 years. The cases are probably not numerous where 
even a much shorter term would necessitate an annual tax levy which would 
be considered excessive. It is obvious that the character of the improve- 
ment will sometimes make the shorter term issues more or less imperative, 
either on general principles or to comply with statutory requirements. 

Corollary to the above principles is adequate provision for maintenance of 
the improvement during its life. The importance of maintenance is so 



BONDS 



273 



great that statutes authorizing bond issues for construction should require, 
as part of the stipulations under which the bonds are issued, an adequate 
financial provision for the upkeep of roads during the term of the bonds. 
This insures a more complete statement of the financial obhgations of a bond 
issue before taxpayers vote on the issue. Maintenance provisions will care 
for depreciation, but not for obsolescence which must be considered in fixing 
the terms of bonds for such improvements as bridges. 

Theoretical discussion of the types of bonds suitable for road improve- 
ment financing usually includes sinking-fund, annuity and serial bonds. 
Practically, however, the annuity bond serves a purpose similar to the serial 
bond, costs shghtly more, and has httle favor either among bond dealers or 
the investing pubHc. These considerations are deemed so important that 
the further discussion of this type has been omitted. 

Under the sinking-fund plan, none of the bonds issued are retirable until 
the end of a definite period and the entire sum raised bears interest for the 
entire life of the bond. The county or municipality pays interest on the 




YCAH8 

NOO.OOO-SOYEAR 4«Io SINKING FUND BONO. 



Fig. 2. — Sinking fund bonds bear interest on full sum for whole life. 



money so borrowed and in addition sets aside each year, as a sinking fund, 
an amount which mvested at compound interest will be theoretically suffi- 
cient to retire all the bonds when they become due. The rate of interest 
usually compounded on the sinking fund is low in comparison with the 
interest paid on the bonds. 

The method of disposing of a 20-year sinking-fund bond is shown graph- 
ically in Fig. 2. 

Under the serial plan a certain amount of the bonds is retired each year, 
the interest on the remaining amount outstanding is paid and the bonds 
retired cease to be an interest charge on the community. The straight serial 
method would require the heaviest payments for interest and retirement of 
principal in the early years of the term issue, often before the improvement 
is fully completed or before it has yielded the community any return. 
To meet these conditions which frequently arise in road districts, the use 
of the deferred serial bond has become common. With such a modified 
type no principal is retired until a certain period, usually five years, has 
elapsed. During this period interest is paid but nothing more. There- 

18 



274 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

after the principal is retired by uniform amounts and tlie interest charges 
are met just as is the case of straight serial bonds having a term shorter by- 
five years, or whatever is the deferred period. In this way the road district 
need not pay anything but interest until the improvements have begun to 
yield a return. 

The straight serial method of payment is graphically shown in Fig. 3. 

For road improvements the serial bond is preeminently the most desirable 
type. The reasons for its special desirability may be briefly stated : 

(a) The serial bond minimizes the dangers involved in the administra- 
tion of a public debt. The serial bond requires annually a specified pay- 
ment of both principal and interest direct to the bondholder. Both principal 
and interest must be met out of the annual tax levy. K the principal pay- 
ment required is not met, there is a public default and community credit is 
seriously injured, if not ruined. The serial bond makes absolutely certain 
gradual retirement of the public debt. 



1,000 




12 3 4 

100.000 -20 YEAR 4«Jo SERIAL BONO. 
Fig. 3. — Serial bonds lessen interest payments. 

Under the sinking-fund plan specified payments for retirement of principal 
must be made to a fund, custody of which is usually vested in pubHc officials, 
until maturity of the debt. Furthermore, the sinking fund must be admin- 
istered so as to earn compound interest. Unfortunately the financial 
methods of public officials do not always remain above criticism and it 
often happens that the annual payment into the sinking fund is forgotten or 
neglected, no matter how much such contingencies may have been legally 
safeguarded. Sometimes the money accumulated in the sinking fund is 
diverted from its purpose. Such departures from sound finance result in 
lack of money to pay off the bonds when they become due, as agreed, and 
it then becomes necessary to issue a new series of bonds to carry the in- 
debtedness. The history of the administration and use of municipal sinking 
funds afford abundant testimony of its dangers. Generally, for most minor 
civil districts, it may be said to be an antiquated and undesirable fiscal 
method. Until a few years ago sinking-fund bonds were almost universally 
used. Realizing the economy of serial issues, about 10 states now require 
serial issues for road improvement issues. 



BONDS 



275 



(b) The serial bond is the cheapest form of bond financing. Figure 4 
presents the relative cost of the different types of bonds graphically and 
Table I presents the actual cost comparison between sinking-fund and 
serial bonds. 

(c) Undoubtedly the serial bond maturing within the life of the improve- 
ment is the most popular bond for private investors and institutions. A 
great many investors will not buy a bond maturing in more than 10 years. 
Serial bonds are attractive because they give the investor an opportunity to 
buy bonds which will meet practically all his requirements as to length of 
time of his investments. For instance, a man may have $4000 or $5000 in 

,340,000 



320,000 



300.000 



280.000 



260.000 



240,000 



220i)00 



200.000 



160.000 



160,000 



140,000 



120.000 



100,000 







^ 










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„ 


TOTAL COST OFA 

100,000 SERIAL BOHO AT 3,4,5, » 6 7» IKTEREST 

100,000 ANNUITY BOND AT 3A.S,5 6<7o INTD?EST 

100.000 SINKINS FUND BOND AT 3,4.5,5 6 "MNTWEST 

PRINCIPAL 5 INTEREST - PAYMENTS MADE ANNUAUY. 

I« SJNK1N9 FUND BEARIMG 3^ 7= COMPOUMDCD ANNUALLy 














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20 2S 30 

TERM IN YEARS 



35 



40 



45 



90 



Fig. 4. — Relative cost of different bond types. 



the bank at a low rate of interest and wants to build or buy a house when 
he accumulates a given sum, say in about 6 years. He is the buyer of a 
6-year serial bond. The same may be true in any number of cases not 
only with private investors, but also institutions. When money rates are 
low, banks are heavy buyers of short term maturities, say, 1, 2 or 3-year 
bonds. When money rates are high and as a consequence, bond prices low, 
the long term bond appeals to the investor. Generally, serial issues enable 
investors to put out their funds in a more satisfactory manner. The dealer 



276 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

can sell them more readily and may, consequently, be able to reduce his bid 
slightly. 

The management of a bond issue requires attention to all the require- 
ments of the laws governing such matters and a knowledge of the conditions 
which affect the value of bonds. Every step which the law requires to be 
taken in connection with such bonds must not only be taken properly but 
recorded fully and clearly. As soon as the voters authorize the issue, a 
statement of the fact should be drawn up, showing also the area, popula- 
tion and assessed valuation of the district, the value of its agricultural and 



Table I. — Comparative Cost — Sinking Fund and Serial Bonds 

Average annual cost of a $100,000 sinking-fund bond bearing 3, 4, 5 or 6 
per cent interest, with sinking fund drawing 33^ per cent interest, and 
bonds maturing at different periods from 5 to 50 years. 



Term in Years 


3% 


4% 


5% 


6% 


5 


$21,648 


$22,648 


$23,648 


$24,648 


10 


11,524 


12,524 


13,524 


14,524 


15 


8,183 


9,183 


10,183 


11,183 


20 


6,536 


7,536 


8,536 


9,536 


25 


5,567 


6,567 


7,567 


8,567 


30 


4,937 


5,937 


6,937 


7,937 


35 


4,500 


5,500 


6,500 


7,500 


40 


4,183 


5,183 


6,183 


7,183 


45 


3,945 


4,945 


5,945 


6,945 


50 


3,763 


4,763 


5,763 


6,763 



Tab-le II 

Average annual cost of a $100,000 serial bond bearing 3, 4, 5 or 6 per cent 
interest, and maturing at different periods from 5 to 50 years. 



Term in Years 


3% 


4% 


5% 


6% 


5 


$21,800 


$22,400 


$23,000 


$23,600 


10 


11,650 


12,200 


12,750 


13,300 


15 


8,267 


8,800 


9.333 


9,866 


20 


6,575 


7,100 


7,625 


8,150 


25 


5,560 


6,080 


6,600 


7,120 


30 


4,883 


5,400 


5,917 


6,434 


35 


4,400 


4,914 


5,429 


5,943 


40 


4,037 


4,550 


5,063 


5,576 


45 


3,756 


4,267 


4,778 


5,289 


50 


3,530 


4,040 


4,550 


5,060 



BONDS 



277 



Table III. — Total Cost of Sinking Fund Bond 

Total cost of a $100,000 sinking-fund bond bearing 3, 4, 5 or 6 per cent 
interest, with sinking-fund drawing 3}i, and maturing at different periods 
from 5 to 50 years. 



Term in Years 


3% 


Ac/ 


5% 


6% 


5 


$108,241 


$113,241 


$118,241 


$123,241 


10 


115,241 


125,241 


135,241 


145,241 


15 


122,738 


137,738 


152,738 


167,738 


20 


130,722 


150,722 


170,722 


190,722 


25 


139,185 


164,185 


189,185 


214,185 


30 


148,114 


178,114 


208,114 


238,114 


35 


157,494 


192,494 


227,494 


262,494 


40 


167,309 


207,309 


247,309 


287,309 


45 


177,540 


222,540 


267,540 


312,540 


50 


188,169 


238,169 


288,169 


338,169 



Table IV. — Total Cost of Serial Bond 

Total cost of a $100,000 serial bond bearing 3, 4, 5 or 6 per cent interest 
and maturing at different periods from 5 to 50 years. 



Term in Years 


3% 


4% 


5% 


6% 


5 


$109,000 


$112,000 


$115,000 


$118,000 


10 


116,500 


122,000 


127,500 


133,000 


15 


124,000 


132,000 


140,000 


148,000 


20 


131,500 


142,000 


152,500 


163,000 


25 


139,000 


152,000 


165,000 


178,000 


30 


146,500 


162,000 


177,500 


193,000 


35 


154,000 


172,000 


190,000 


208,000 


40 


161,500 


182,000 


202,500 


223,000 


45 


169,000 


192,000 


215,000 


238,000 


50 


176,500 


202,000 


227,500 


253,000 



industrial products, its material resources and the extent of their develop- 
ment, the banking and transportation facilities serving it, the existing in- 
debtedness of the district, the condition and number of the schools, and all 
other information which will indicate the resources and character of the 
community that has decided to borrow the money. This information should 
be sent to banking houses and insurance companies making a specialty of 
purchasing public bonds and, if the issue is a large one, it should be adver- 
tised in financial journals. There should be ample time between the pub- 
lication of these notices and the sale of the bonds for purchasers to make a 
full investigation of them. 



278 LOCATION, GRADING AND DRAINAGE OF HIGHWAYS 

^ Private sales of bonds for public works should be discouraged, all sales 
of bonds should be pubhcly advertised, and bidders should be in^-ited to 
submit sealed bids on or before a certain date. The bonds should be sold 
to the highest responsible bidder who compHes with all of the terms and con- 
ditions of the sale. The city or county should reser\*e the right to reject any 
or all of the bids, as a protection against any effort to pool bids and purchase 
the bonds at a price considerably less than their value. 

Some cities and counties engage competent attorneys, famihar with the 
preparation of the legal papers pertaining to bond issues, to examine the 
records prior to the sale and prepare all necessary forms. The city or county 
assumes the expense for all such work and furnishes the successful bidder 
with the approving opinion of the counsel thus engaged and with the 
executed bonds. Some cities and counties go even further by pro^dding 
uniform proposal blanks for the bonds and refusing to accept bids not made 
on such blanks. The advantage of these provisions is that the seller knows 
he is offering a legally and vahdly issued bond, the buyer has the same 
assurance, and the value of the issue is certainly enhanced thereby. The 
seller is undoubtedly reimbursed for the expense incurred in such preparatory 
work by the price he receives for the bonds. 

^ This and the next paragraph were prepared by Baker, Watts & Company. 



INDEX 



General Note. — The page references are given in their order of im- 
portance. The first reference will usually cover the most used data. 

Page 

Alignment (General Discussion) 133 

At bridge approaches ( minimum radius) 147, 149, 65, 137 

" hairpin turns (switchbacks) 140, 145-146 

railroad grade crossings 147 

Dangerous alignment 134 

Effect on construction cost 142 

" " crown of pavement . 165-167, 133, 17 

'' " grade 138 

" " location surveys 149, 147, 133 

" " motor operation cost 141 

" " sight distance 134 

" width of pavement . 165, 17 

" " width of right of way 210 

" " width of section 134, 135 

Encroachment of long wheel base rigs 138, 140 

Minimum radii (current practice) 136 

Minimum radii (recommended practice) 147 

Principles of location 149 

Sight distance requirements 134, 141 

Switchback alignment 140, 145, 146 

Summary of alignment practice 147-149 

Annual Charges 

Bonds for construction 271, 20 

Maintenance and renewals 51 

Tax rates (1920) 51-54 

Annuity Highway Bonds 272 

Apportionment of Funds 41 

Appropriation Estimates 

Classifications for 46-50 

Value of careful engineering estimates 1 

Arch Bridges (Small Span) 

Economical Use 233 

Typical example 236, 261 

Artillery Loads (Military) 231 

Automobiles (Their Effect on general policy and detail design) 

Character of Traffic 

Range of travel (local and long distance) 10, 38, 56 

Speed, regulation of 12, 13 

Types of hauling .♦ 10-12 

279 



280 * INDEX 

Page 

Automobiles (Cont.) 

Volume, growth of 69 

A'olimie, comparative amount local 10 

Weight, regulation of : 10-13 

Cost of Operation 

Effect on aUgnment 141. 149 

grade design 79-114, 148 

" location problems 60, 148 

Inefficient operation 91 

Emergency Stops 134 

License Fees 

Amount required 51-55 

Reasonable use for 52, 8, 22 

Safety of Operation {Requirements of) 

Cur^'es, easy ahgnment 147, 134 

, superelevation 167, 17 

Crown, '■ one way "' 183 

Ditches, shallow 158. 209, 17 

Guard rail 17, 151, 152, 232 

Pavement widening 165, 17 

Railroad crossings, ehmination of 147. 17 

Section, shape and width 151-199, 17 

Sight distance 134, 17 

Signs, danger and guide 17 

Vertical curves 131 

Tax Burden {General Principles) 52, 8, 22 

Trucks 

General effect on design 60, 12 

" " pohcy 9-12, 3-4 

Operative costs 7^114 

Performance on grades 80, 83 

Regulation of (speed, weight, height, length) 12, 13, 140, 9, 4 

Tax burden for unusual refinements of construction 8, 60, 62, 4 

Tj'pes suitable for various uses 11 

Banked Curve Sections 

Grading shapes 180 

Layouts at curves 167, 180 

Pavement superelevation 167, 180 

width 165, 169 

Beautifying the Highway (Tree Planting) 209 

Bituminous Macadam 

Depths recommended (differen t soils) 180 

Proper use of flexible pavements 

Location 43, 7, 8, 15, 16 

Extent (examples) '. 15, 46 

Tj'pical sections 168-180 



INDEX 281 

Page 

Bonds (Highway) 

Cost of, total cost 271-277, 20 

" " , yearly budget 271-277, 20 

Marketing 275 

Term, effect on cost 271-277, 20 

" , " "design 20 

, reasonable length , 20, 271 

Types of bonds (general dicussion) 

Annuity 272 

Serial 272, 273 

Sinking fund 272, 273 

Brick Pavement 

Proper use of rigid pavements 

Location 43, 7, 8, 15, 16 

Extent (example) 15, 46 

Typical sections 168-181 

Bridges 

Approach aUgnment 147, 149, 65, 137 

Loads 230 

Roadway widths 231 

Types, economical 233, 248 

Waterway area 218 

Bridges (Small Span) 

Design (general considerations) 212, 248 

Foundation soils 248 

Piles (use of) 248 

Scour 262 

Types, examples of 249-261 

" , selection of 233, 248 

Biirkle-Ziegler Runoff Formula 221 

Capacity of Culverts 223 

" " Ditches ^ 262 

Cast Iron Pipe Culverts (See also Culverts) 242, 238 

Catch Basins (Example of) 266 

" (Use of) 265 

Classification of Roads 

For design and pavement selection 

By location 43, 15 

By traffic census • 43 

Examples of 46 

For financing 

National Roads 41 

State " 42 

County " 42 

Town " 42 

Appropriation estimates 46-50 



282 IXDEX 

Page 

Classification (Cont.) 

For maintenance and renewal 46-52 

Example of 51 

Clearing (Trees and Brush i 

Objects of 211 

"Widths of 211 

Cobble Gutter 264-265 

Concrete Culverts 212-247 

Design of 

Area of waterway 218 

Cleaning , 226 

Concrete (mix used) 238 

Cushion over top 230 

Discharge capacity 223. .266 

Invert elevation 229 

grade 229 

Length 231 

Loads 230 

Location layouts 214, 267 

Roadway width 231 

Special conditions 227 

Types in use 

Examples 240-247 

Selection of 238, 233 

Concrete Guard Rail 

niustrations of 152, 228, 232, 29 

Proper use 151, 17 

Concrete Pavement 

Reasonable use of rigid pavement 

Location 43, 7, 8, 15. 16 

Extent (example) 15. 46 

Typical sections 168-181 

Concrete Pipe Culverts (See also Culverts) 238, 243, 267 

Contracts 

General pohcy 23 

Length of 24 

Corrugated Metal Pipe Culverts (See also Culverts) 

Example of 241, 238 

Use in drives 267 

Cost of Bond Financing 271, 20, 50 

Cost Estimates (Preliminary) 

For construction programs 

Classifications 42-49 

Value of engineering estimates 33, 1 

For maintenance and renewal programs 

Classifications 42-49 

Example 51 



INDEX 283 

Page 

Cost of Motor Operation (See also Automobiles) 

Effect on location and grade design 79-114, 141, 148 

Weight given to tiiis factor in the design of highways 60 

County Roads (Classification and Extent) 42 

Cross Sections (See Sections) 

Crowns (Pavement) 

"Banked" crowns on curves • 167, 193 

Effect of grade 182 

Effect of pavement width 153 

Effect on convenience of travel 153, 183 

*' " maintenance 153 

Examples of current practice 168-178 

'' '* recommended 153, 179-181 

"One way" crown 183 

Superelevation on curves 167, 193, 180 

Culverts 

Cost comparative 238 

Design of 212-239 

Area of waterway 218 

Cleaning 226 

Cushion over top 230 

Discharge capacity 223 

Invert elevation 229 

Invert grade 229 

Length 231 

Loads 230 

Location layouts 214 

Roadway width 231 

Special conditions 227 

Types in use 233 

Examples 233-247 

Selection of 233, 238 

Driveway culverts 266 

Length 267 

Location 267 

Size 267 

Types 267 

See also, (cast iron pipe) 

" , (concrete culverts) 
" , (concrete pipe) 
" , (corrugated metal pipe) 
" , (log culverts) 
*' " , (vitrified tile culverts) 

Curves 

At bridge approaches (minimum radius) 147, 149, 65, 137 

hairpin turns (switchbacks) 140, 145-146 

Dangerous alignment 134 



284 INDEX 

Page 

Curves {Cont.) 

Effect on construction cost 142 

" crown 16.5-167. 133, 17 

" " grade 138 

location surveys 149, 147, 133 

motor operation costs 141 

sight distance 134 

width of pavement 165, 17 

nght of way 210 

" section 134, 135 

Encroachment of long wheel base rigs 138, 140 

Mininumi radii (current practice) 136 

" " (recommended ") 147 

Principles of location 149 

Sight distance 134, 141 

Switchbacks 140, 145, 146 

Summaiy' of ahgnment practice 147-149 

Vertical curves 131 

Minimum length 131-132 

Proper use 131 

Danger (Elimination of) 17 

Ahgnment practice 149, 147, 134-147 

Banked curves 167. 17 

Ditches (shallow) 157, 17, 209 

Grade (safe descent) 71, 80 

Guard rail 151, 17 

" One way " crown 183. 151 

Pavement widening 165, 17 

Railroad crossings 147, 17 

Sight distance 134 

Traffic clearance (safe width) 156, 164-165 

Warning signs 17 

Danger Signs 

General use of 17 

Depreciation of Pavements (General) 22, 271 

Depths of Pavements (Thickness) 

Macadam on different soils 180 

Rigid pavements (examples of typical sections) 168-181 

Design of Highways (General) 

Economy in 31 

Fundamental considerations 4-27 

G^eneral tests of 33 

Locations 59-67 

Proportion in 28-31 

Design of Highways (Detail Practice) 

Ahgnment 133-150 

Classification for financing and design 40-52 



INDEX 285 

Page 

Design (Cont.) 

Drainage 212-270 

Grades 68-133 

Layout of main road systems 38-40 

Locations 59-150 

Relocations 64 

Routes (selection of) 55 

Distance (Value of Saving) 63, 86, 96-107 

Principles of location 149 

Ditch Protection (Gutters) 264-266 

Ditches 

Capacity of 262 

Dangerous 158 

Depth of 157, 17 

Flow of water in. ! 262 

Functions of 157 

Intercepting 193, 178, 262 

Protection of (gutters) 264-265 

Relief culverts and storm sewers 216, 265 

Safe ditches 151, 154, 17, 209 

Drainage 

Bridges (small span) 248-262, 212-248 

Culverts 212-248 

Ditch reHef culverts 216, 265 

Ditches 157-159, 262-265, 17 

Driveway culverts 266 

Low water culverts 227 

Special conditions 227 

Storm water sewers 265 

Underdrains 267 

Driveway Culverts 266 

Economy in Design (General) 

Desirability of 31 

General principles of 4-27 

Limitations of 34, 61, 213, 270 

Tests of design 33 

Economy in Design (Details) 

Alignment (effect on construction cost) 142 

Drainage (economical types) 233, 238, 267 

Grades (effect on construction cost) 

Adverse 130 

Intermediate 126-129 

Maximum 118-120 

Minimum 130 

Vertical curves 129, 131 

Grading widths (effects on construction cost) 159 

Location ( " " '' " ) 148, 150, 29, 59 



286 INDEX 

Page 
Economy in Design (Cord.) 

Materials (proper use of) ... ; 17 

Pavement type 162, 14 

" width 162, 15 

Embankments (See Excavation) 

Encroachment of Rigs on Sharp Curves. . . ; 138 

Engineering (Highway) 

Function of 1-4 

Value of 33, 2 

Excavation 

Amounts required (general comparative) 

Cut and fill profile design 120-125 

Side hill balanced sections 200-208 

Effect of alignment . •. 142 

*' " grading width [ 159, 183 

intermediate grades 126 

" maximum grades 118 

" " slopes 160 

Slopes (stable) 160 

Fees (Auto License) 

Amounts required 54, 51 

Proper use of 52, 8, 22 

Tax burden distribution 52 

Fills (Embankments) 

Stable slopes 160 

Widths 168-199 

(See also excavation) 
Financing Highway Improvements 
Bonds (see also bonds, highway) 

Cost of bonds 271-277, 20 

Reasonable term 20, 271 

Types in use 272, 273 

Effects of methods of financing on design • 20 

General policy 8, 20, 271-277 

Tax burden distribution (general) 52 

Tax rates (1920) 51, 54 

Flood Runoff (Small Watersheds) 218-226 

Flow of Water in Ditches 262 

Foundations (Culverts and Bridges) 248 

Girder Bridges (Reinforced Concrete) 248, 233, 258, 236 

Grade Crossings (Railroad) 

Alignment at ' 147 

Ehmination of 147, 17 

Grade at 147 

Grades 68-133 

Adverse Grades 130 



INDEX 287 

Page 
Grades {Cont.) 

Intermediate Grades .- 125-129 

Controlling points 125-126 

Economic design 

Effect on construction cost 126 

" " horse traffic 126 

" "motor " 126,113,79-114 

"Rolling" grades 126-129, 150 

Principles of locations 150, 132 

Maximum Grades 71-125 

Current practice , 115 

Economic design 

Effect on construction cost 118 

horse traffic 71-79 

" '' motor " 79-114 

Recommended practice 116 

Effect of alignment 138 

'' " length of grade 77, 112 

" safety of descent 71, 80 

" team footing 114 

Principles of location 148 

Mimimum (Level) Grades 129 

''Rolling" Grades 126-129, 150 

Village Grades 126 

Grading 

Amount required (general comparative) 120-125, 200-208 

Economical design 33 

Effect on cost 33, 142, 159, 183, 126, 118, 160 

Shapes of 168-182, 194-199 

Slopes (stable) 160 

Width of 151-208 

(See also excavation) 

Gravel Roads, General Suitability 7, 15, 43 

Grubbing (See Clearing) 

Guard Rail. , 17, 151, 152, 232 

Gutters 264-265 

Hauling 

Horse traffic 

Loads on different grades 75-79 

Motor traffic 

Cost-of 79-114 

Effect of alignment 141 

" " distance 63, 79-114 

" " grade 79-114 

" " rise and fall 79 114, 63 

Limitations of 70 

Suitable conditions for different types of motor 10-12 



288 INDEX 

Page 
Highway Bonds (See Bonds) 

Horse Traffic 

Ascent and descent 71 

Considerations of, in general policy 10, 70 

Footing 114 

Loads on grades 75-79 

Tractive effort long and short grades 72, 77 

Volume, change in 69 

Intercepting Ditches 193, 178, 262 

Investigations 

Preliminary, general value 35, 40 

Traffic 43 

Land Taking (Right of Ways) 208 

Life of Pavements (General Comparative) 22 

Loads 

Bridge Design 230 

Regulation of (vehicles) . . . 12, 13, 9 

Wheel loads 

Military 231 

Trucks 12 

Location of Roads 

Engineering Location 

Detail principles, summary of 148 

General " 59 

Layout of Systems, general principles 38 

Route selection, general " 55 

See also alignment 
" '' grades 
Log Culverts 240 

Macadam (See Waterbound and Bituminous Macadam) 

Depth recommended (different soils) 180 

Proper use of flexible pavements 

Location 43, 7, 8, 15, 16 

Extent (example) 15, 46 

Typical sections 168-180 

Maintenance 

General Problem ' • 24 

Preliminary finance estimates 51 

Materials 

Economic use of 17, 33 

Maximtun Grades (See Grades) 

Military Wheel Loads 231 

Minimum Grades (See Grades) 



INDEX 289 

Page 

Motor Traffic (Its Effect on General Policy and Detail Design) 

Character of traffic 

Range of travel (local and long distance; 10, 38, 56 

Speed, regulation of 12, 13 

Types of hauling 10-12 

Volume, growth of 69 

" , comparative amount local 10 

Weight, regulation of 10-13 

Cost of operation 

Effect on alignment 141, 149 

" grade 79-114, 148 

" " location 60, 148 

Inefficient operation 91 

License fees 

Amount required 51-55 

Reasonable use of 52, 8, 22 

Emergency stops 134 

Safety of operation (requirements of) 

Curves, easy alignment 147, 134 

" , superelevation 167, 17 

Crown, " one way " 183 

Ditches, shallow 158, 209, 17 

Guard rail 17, 151, 152, 232 

Pavement widening 165, 17 

Railroad crossings, elimination of 147, 17 

Section, shape and width 151-199, 17 

Sight distance 134, 17 

Signs, danger and guide 17 

Vertical curves , 131 

Tax burden (general principles) 52, 8, 22 

Trucks 

General effect on design 60, 12 

" " " policy ' 9-12, 3-4 

Operation costs 79-1 14 

Performance on grades 80, 83 

Regulation of 12, 13, 140 

Tax burden for unusual refinements of construction 8, 60, 62, 4 

Types suitable for various uses 11 

Mountain Roads 58, 116, 142-146, 182-208, 211, 216 

Operation Cost of Motor Vehicles 

Comparative cost on different grades 96-105 

Effect of alignment 141 

" distance 86, 105 

" grade , . . . . 79-114 

Inefficiency of operation 91 

Pavements 

Cost of, general comparative 1 63 

19 



290 INDEX 

Page 
Pavements (Cont.) 

Crowns 

Normal 153 

Superelevation on Curves 167 

Depreciation of (general comparative) 22 

Design classification 42-50 

Life of, general comparative 22 

Maintenance, general problem 24, 51 

Thickness (example of) 

Macadam and gravel 180 

Rigid pavements 168-181 

Sand clay 173 

Type 

Classification of roads for 42-50 

Effect of local materials 17, 33, 14 

" " finance methods 8, 20, 271, 272 

" " traffic requirements 10-13, 14-17, 42-50 

" " general character of the territory served 7, 8, 43, 14-17 

General suitability of 14-17, 43 

Relative of extent of necessary use (example) 46-50 

Widths 

Effect on cost 163, 33 

Extra at sharp curves 165 

Normal widths 163 

Pile Trestles (Examples of) . 253, 259 

Piles 

Loading 248 

Use of 248 

Pipe Culverts 

Design (see culverts) 

Discharge capacity 223, 266 

Examples of 

Cast iron pipe 244 

Concrete pipe 243 

Corrugated metal 241 

Vitrified tile 242 

Use of 

Economic 238 

Limitations ' 238, 219-229 

Plans 

Economic design 

Alignment 133-150 

Ditches 159-160 

Drainage 212-270 

Grades 68-132 

Location 148 

Materials 17, 33 



INDEX 291 

Page 
Plans {Cont.) 
Widths 

Grading 151, 159, 183 

Pavements 151, 162 

Standardization (value and limitations) 35 

Tests of (general) 33 

Preliminary Appropriation Estimates 

Classifications for 40-50, 1 

Example of 49 

Importance of care in their preparation 1, 49 

Value of engineering 1 

Preliminary Investigations 

General value of 35, 40, 1 

Traffic counts 

Limitations of 43-46 

Value of 43-46 

Profile Design 

Economic principles of 150 

Grades 

Adverse 130, 150 

Intermediate 125-129, 150 

Maximum 71-125, 150 

Minimum 129 

''Rolling" 126-129, 150 

Vertical curves 

Minimum length. 131, 132 

Use of 131 

Radii of Curves 

Effect on cost of construction 142 

*' << " << motor operation * 141 

" crown 165-167, 133, 17 

" " encroachment of rear wheels 138-140 

" " grade 138-140 

" " safety of travel 147, 134 

" " shape of section 151-199,17 

" " sight distance 134 

width of payment 165, 17 

" " " " right of way 210 

" "section 134,135 

Recommended practice 147 

Switchback turns 140, 145, 146 

Railroad Crossings 

Alignment and grade at 147 

Elimination of 147, 17 

Rainfall 218-220 

Regulation of Traffic 9, 12-13, 140 

Repair of Pavements, General Problem 24, 51 

Right of Way 208 



292 INDEX 

Page 

Rip Rap 262 

Road Materials, Economic Use 17 33 14 

Road Sections, Typical (Example of) 168-182,194-199 

Road Systems 

Classification 40-52 

Financing (bond method) 271-278, 20 

Layout and route selection 38, 55 

Scope 40-42 

Tax burden 52, 8 

Tax rates (1920) 51, 54 

Traffic requirements 3-17 

Roadway, Traveled Width of 153-157 

Ruling Grades, (See Grades) 

Runoff (Small Watersheds) 218-226 

Safety Measures 

ALgnment 147, 149, 134 

Banked curves 165-167, 17, 151 

Ditches, shallow 157, 17, 151, 209 

Grades, compensated 138 

Guard rail, use of 17, 151, 152, 232 

Railroad grade crossings 147, 17 

Shoulder slope 153. 8, 154 

Sight distance 134, 147, 149 

Signs, warning 17 

Widths of pavement 163-165 

" " section 151-199 

Scour 

Ditches, protection of 264 

Rip rap, use of , . 262 

Velocities producing scour 264 

Sections of Roadway 

Design of 151-211 

Examples of 168-182, 194-199 

Shoulder 

Slopes 153, 168-182 

Stone or gravel protection 163, 179 

Widths of 157, 168-182 

Sight Distance 

Effect on alignment 149, 147, 135 

'' " grades 149, 142 

" " grading 135, 136 

" " motor operation cost 141 

" " right of way widtlxs 210 

Safe sight distance 134 

Vertical curv^es 131 



INDEX 293 

Page 

Signs 

Guide, use of 17 

Warning '' " 17 

Slopes (Stable) 

Cut and fill 160 

Snow 

Effect on locations 60, 211 

Soils 

Bridge foundations 248 

Effect on depth of macadam 180 

" " type of underdrain 267 

" " on locations 148 

« " slopes 160 

Speed of Trucks (Regulation) '. 12, 13 

Stream Runoff (Flood) 218-226 

Stream Scour 262 

Taxes, Highway 

Distribution of, general principles 52, 8, 22 

License fees 54 

Prevailing rates, property tax 51 

TUe, Vitrified (See Vitrified Tile Pipe) 

Tile, Underdrains ." 267 

Tires, (Wagon or Automobile) 

Allowable load per inch width 12, 13 

Effect of width on tractive resistance 74 

Tractive Power (Horses) 72 

Traffic 

Census of 43 

Character of 9-13 

Classification for 46 

Operation cost 

Effect on alignment 141 

" *' grades 79-114 

" " location 79-114, 60 

Range of (local and long distance) 10, 38, 56 

, Regulation of 9, 12, 13, 140 

Requirements of 3-17 

Safety of 

Effect of alignment 147, 149, 134 

" ditches 157, 17, 151, 209 

'' " guard rail 17, 151, 152, 232 

" '' grades 138, 71, 80 

** " sectional widths and shapes 151-199 

" " sight distance 134, 147, 149 

" " warning signs 17 



294 INDEX 

Page 

Traffic {Cont.) 

Tax burden on 52, 8, 22 

Volume, change in 69 

Trucks (See Automobiles) 

Underdrains 

Cobble 268 

Tile 268 

Minimum fall • 26 

Vertical Curves 

Minimum length 131-132 

Use of 131 

Vitrified Pipe Culverts 
Design of {see culverts) 

Discharge capacity 223 266 

Economic use 238 

Examples of 242 

Weights and dimensions 242 

Wagon Loads 

On different grades 75 

Farm wagon loads 115 

Mountain freighting loads 78 

Warning Signs (General Value) 17 

Waterbound Macadam 

Depreciation (general comparative) 22, 272 

Depths on different soils 180 

Life of (general) 22 

Typical sections (examples of) 168-180 

Use of macadam 

General suitability of type 43, 7, 8, 15, 16 

Extent of probable use (examples) 15, 46 

Waterway of Culverts 

Determination of size 218 

Wheel Loads 

Military ordinance 231 

Regulation of loads 9, 12, 13 

Trucks , 12, 13 

Widths 

Of bridge and culvert roadways 231 

Of pavements 162-166, 15-17 

Of right of way 210 

Of sections 153-160, 183, 168- 182, 194-199 

Of travelled way 153 

Yearly Appropriations (Preliminary Estimates) 

Bond charges for construction 271-278, 20 

Maintenance and renewal financing 

Value of classification 51 



